Women and Minorities in Antarctica

Accounts from under-represented groups and their relationships with Antarctica are still rarely acknowledged in stories about the continent’s human history[1]. Instead, there is a continued focus on the heroic era with mainly European male explorers.

Whilst still critically important, literature is filled with their accounts, and therefore this page will focus on the encounters from under-represented groups, and how they have all played a part in the discovery of Antarctica, and have helped make it the place it is today.

You can explore the history of Antarctica more in our interactive StoryMap.

The Māori discovery of Antarctica

Māori carvings at the New Zealand’s Scott Base in Antarctica. Antarctica New Zealand.

Recently, Weihi et al. (2021) [1] attempted to uncover more about these important, yet invisible groups and their links to Antarctica. They collated evidence from grey literature and oral histories to highlight the Māori presence.

Their findings suggested that the Māori people may have been the first group to discover Antarctica’s waters. This could have been as early as the seventh century. 

The Kāhui Māori (Māori advisory group) are now working with New Zealand’s Antarctic teams to help spread more information on early Polynesian and Māori exploration to the Antarctic Region. Their work is also going to help support more Māori communities, including Māori researchers [2].

Men weren’t the only ones exploring Antarctica

Louise Seguin: 1773

In 1773, the same year as Captain Cook voyaged to the Antarctic Circle, was the first record of a western woman to cross into the sub-Antarctic region [3]. Her name was Louise Seguin, and she travelled with her husband Captain Yves Joseph de Kerguelen.

Women were not allowed to join on these voyages, and her husband was later court-martialled for bringing her. Following this event, women made infrequent appearances with their husbands on voyages, however were rarely acknowledged due to the sociopolitical timings of these events [3].  She must have been a very brave lady to contravene society’s expectations at this time.

Abby Jane Morrell: 1833

Abby Jane Morrell was one of the first woman in Antarctica
Abby Jane Morrell. One of the first women in the Discovery of Antarctica

Abby Jane Morrell set sail on the Schooner Antarctic with her husband Benjamin Morell in 1833. What is significant about Abby’s journey to the sub-Antarctic region was that she had a written account of her trip. These included stories about meeting native communities, deaths on board the ship and the wildlife they had encountered [4].

This was the first written account of a woman within the sub-Antarctic region. Her husband also journaled through the trip and for many years his overshadowed of that written by Abby [3]. 

Ingrid Christensen: 1931

In 1931, Ingrid Christensen became the first woman to lay eyes on Antarctica alongside her companion – Mathilde Wegger [5]. She visited Antarctica four times on the Thorshavn and was involved in resupplying the other fleet of ships, including her husbands. Ingrid’s story does not stop there.

Several years later in 1937 Ingrid became the first woman to see Antarctica by air, and later that year brought her daughter, Sofie (18) to Antarctica. However Ingrid was not the first woman to step foot onto Antarctica.

The loss of masculinity?

Caroline Mikkelsen was the first woman to set foot onto Antarctica during the discovery of Antarctica
Caroline Mikkelsen was the first woman to set foot onto Antarctica. GCT

According to historic newspaper articles, the first step onto the Antarctic continent by a woman meant that Antarctica lost its title of being the ‘world’s last stronghold of masculinity’ [6].

This article was written about Caroline Mikkelsen who in 1935 was the first woman to make land on Antarctica [3,6]. This was over 100 years since the first man.

Caroline’s adventure to Antarctica was kept under wraps for some time following her trip, even after her husband’s death [6].

History is made by George Washington Gibbs Jr.

George Washington Gibbs Jr
George Washington Gibbs Jr.

1940 was the first known year that an African-American male visited Antarctica. George Washington Gibbs Jr. set sail on the Admiral Richard Byrd’s voyage after being chosen from hundreds of applicants to join an expedition to Antarctica.

George Washington Gibbs Jr. was hired as a mess attendant and also trained as a cook. Accounts taken from his journal explained that he was often treated badly by officers on board the boat, but spoke highly of the Captain, who welcomed him as the first African-American to set foot on Antarctica [7,8].  

Through his work in Antarctica, as well as later service to the American forces during World War II, he was awarded a series of medals, and also was promoted to Chief Petty Officer [8].

The first women to overwinter in Antarctica: 1946-1948

Between 1946 and 1948, American women Jackie Ronne and Jennie Darlington were the first women to over-winter in Antarctica, and spend a full year in Antarctica [2]. They helped other members of their team establish a US research station on Stonington Island.

Similarly to every other account we have spoken about on this page, both Jackie and Jennie faced criticism from their male team members. These same team members also signed petitions to refuse Jackie’s and Jennie’s entry to Antarctica [3]. 

A Progression to more women in Antarctica

It was only in 1969 that the US Navy lifted its ban on transporting women to Antarctica. Following this, the National Science Foundation (NSF) finally allowed women to work on scientific expeditions organised by them. Prior to this, women would have to use different funding options to conduct science in Antarctica and typically because of these constraints, they would not normally be hired over men.

After the lifting of these bans, Antarctica saw a gradual increase in the number of women who worked in Antarctica. Elena Marty and Jan Boyd in 1974 became the first woman to be given administrative roles.

Dr Michele Eileen Raney in 1978-9 was the first American woman physician work all year round in the South Pole [3]. After more progressive years, women were gradually able to take up higher roles such as station leaders and aviation leaders.

More recent events in Antarctica

First Black woman to reach the South Pole

The first black woman in Antarctica
Barbara Hillary. BlackPast

‘Antarctic firsts’ are still happening today. As more and more people are visiting Antarctica it gives the opportunity for more milestone events to occur. For example, Barbara Hillary who was the first African-American woman to reach the South Pole in 2011, she was 79 at the time of her arrival. Barbara is also known as the first African-American who reached both Poles.

2012 International Women’s Day

Professor Dame Jane Francis
Professor Dame Jane Francis

On the 2012 International Women’s Day, Antarctica saw ore than 50 women celebrating. They made up 70% of the International Antarctic Expedition.

A recent key milestone event was Professor Dame Jane Francis becoming the first female director of the British Antarctic Survey (BAS) in 2013.

Antarctic Pride

The first ever Antarctic Pride event was held in 2018 and it was celebrated at the US McMurdo Station.

Preparations began in early April before Antarctica faced 24 hours of darkness during their winter. Since this initial event, each year the celebrations have gotten bigger and bigger. In 2019, a flag was brought to the top of one of South Georgia’s Mountains.

Dr Kat Ganly was working within the Antarctic region from 2019-2020 and experienced the two pride events, both South Georgia’s first Pride in 2019, and the inaugural Polar Pride celebration in 2020. She has written a reflection which can be found here.

Pride flag in South Georgia. Photos taken by Jerry Gilham.

Looking Forward

There is no doubt that there are many more encounters from other under-represented groups who have been part of the discovery of Antarctica and have not been included within this page, or even discovered yet. However, bringing to light their accounts will not only help historians better understand the migrations to the southernmost continent, but it will also emphasise Antarctica’s deep cultural roots, which should be shared and talked about.

This page has highlighted predominantly women’s stories and their trips to Antarctica or its surrounding waters, but have only touched the surface on other under-represented groups such as those in the BAME or LGBTQ+ communities. Information for these different groups are not as readily available as those of women, so we are calling for anyone to contribute by commenting different resources where we can find more information about these groups in Antarctica to help spread their stories!

We have highlighted the gradual progression to more inclusion of under-represented groups, however there is a lot more that can still be done.

For more information and resources about ethnic minority groups within the polar science community, check out the Polar Impact website.


[1] Wehi, P.M., Scott, N.J.., Beckwith, J., Rodgers, R.P., Gillies, T., Uitregt, V.V., and Watene, K. (2021) A short scan of Māori journeys to Antarctica. Journal of the Royal Society of New Zealand. DOI: 10.1080/03036758.2021.1917633

[2] Antarctic New Zealand (2020). ‘Kāhui Māori to protect and guide Antarctic as well as climate adaptation research’. Available at: https://www.antarcticanz.govt.nz/media/news/kāhui-māori-to-protect-and-guide-antarctic-as-well-as-climate-adaptation-research. (Last accessed 24th September 2021).

[3] Hulbe, C., Wang, W., and Ommanney, S. (2010) Women in glaciology, a historical perspective. Journal of Glaciology. 65(200). pp. 944-964.

[4] Duneer, A.J. (2010) Voyaging Captains’ wives: Feminine Asethetics and the uses of Domesticity in the Travel Narratives of Abby Jane Morrell and Mary Wallis. Journal of the American Renaissance. 56(2). 192-230.

[5] Blackadder, J. (2015) Frozen Voices: Women, Silence and Antarctica. In Hince, Bernadette; Summerson, Rupert; Wiesel, Arnan (eds.). Antarctica: Music, Sounds, and Cultural Connections. Canberra: ANU Press.

[6] 5. Joanne, P. (2018) First Women in Antarctica. Available at: https://medium.com/@BLBookReviews/first-women-to-antarctica-cc80060650fb (last accessed 19th September 2021).

[7] Rejcek, P (2010) Making History. Available at: https://antarcticsun.usap.gov/features/2268). (Last accessed 19th September 2021).

[8] Stein, G.M. (2010) The first African-African in Antarctica: George W. Gibbs Jr. Polar Record, 46(3). 281-282. doi:10.1017/S0032247409990507

Tourism in Antarctica

This article about Antarctica’s tourism has been written by Laura Boyall and Benjamin Samingpai.

A trip to Antarctica is not a common holiday destination for many people. However, since the 1950s, there has been a growing number of individuals travelling to the southernmost continent. And then from the 1980s, the growth has been exponential with a 600% rise in travellers [1]. Each season Antarctica sees approximately 170,000 visitors from mostly English-speaking countries. However, there has been a recent rise in the number of tourists from China [2,3]. Click on the figure below to explore how Antarctica’s tourism changed in the 2018-2019 and 2019-2020 seasons.

Pie chart of Antarctica's tourists nationalities

Since the signing of the Antarctic Treaty in 1959, Antarctica has been designated as a place of peace and science, so this recent rise in tourism in Antarctica has sparked some debate about how sustainable tourism is. This article explains some of the steps which are taken to reduce the environmental impact of Antarctica’s tourism to ensure that more and more people can visit and see this unique icy continent [4].

Quark Expedition vessel in the background of two penguins. Quark are an Antarctica's tourism provider
Quark Expeditions vessel and two penguins. Derek Oyen

Managing Antarctica’s Tourism

Penguins huddling on some sea ice to see when partaking in Antarctica's tourism
Group of penguins on sea ice. Danielle Barnes

All human activity, including tourism in Antarctica, is governed by the Antarctic Treaty. This means that a set of rules and regulations are in place to manage Antarctica’s tourism to limit the environmental impacts on the continent [5]. An example of how tourism has been managed is the signing of the 1991 Protocol on Environmental Protection, which came into effect in 1998 [6]. Alongside other important environmental rules laid out in this protocol, such as waste disposal and marine pollution, this protocol specifically ensures that popular tourist sites are safe and environmentally protected.

The International Association of Antarctica Tour Operators (IAATO)

IAATO Logo. Antarctica's Tourism Industry's largest operator

The International Association of Antarctica Tour Operators (IAATO) are the main tourism body for Antarctica, which are made up of seven of the largest Antarctic tour operators [7]. IAATO have a series of sustainable goals which are in line with the Protocol on Environmental Protection such as a limited impact on the Antarctic environment, they help spread awareness of environmental issues, and support Antarctic science with logistical support and research.

Sustainable Tourism Activities

Fluking right whale

There is a whole host of activities that tourists can do in Antarctica including water sports, wildlife excursions and mountain climbing, but there are also activities that help ongoing scientific research. This typically comes in the form of citizen science projects, but can also be helping with logistics, such as helping deliver equipment and supplies to researchers. There are a number of these projects available such as HappyWhale where tourists can upload images of whales they have spotted and their location to aid understanding about species distribution and numbers [8,9].

How Antarctica’s Tourism may not be Sustainable

Despite the sustainable procedures in place, tourism in Antarctica does have some environmental implications. Tourism in Antarctica typically occurs during the summer months (November to March) as it is when the sea ice surrounding the continent is at its minimum, allowing cruise ships to pass through with ease. However, this is when Antarctica is most sensitive with surface melt and ice shelf thinning at its highest, and ice accumulation at its lowest [10].

Threat to Antarctica’s Wildlife

The primary threat of humans visiting the most secluded continent on Earth is the introduction of alien species to its ecosystems. Seeds, bacteria and spores can enter Antarctica from items of clothing and equipment which can lead to the spread of invasive plant species and pathogens [11]. It is estimated that tourists can bring up to 9.5 seeds per person to Antarctica [14]. However, many tour operator staff are required to deep clean passengers belongings before they can step onto Antarctica.

Sinking ship MS Explorer on the 27th November 2007 threatened Antarctica's Tourism industry
Sinking MS Explorer. Wiki Commons

In addition to this, vessels visiting Antarctica’s waters can sink and release harmful toxins and fuels to the ocean, putting Antarctica’s ecosystems at risk. An example of this is the sinking of the MS Explorer within the Drake Passage on the 23rd November 2007 after colliding with an iceberg. Whilst all crew and passengers were saved, the environmental impacts of this can still be seen today. As the vessel sank, it released petroleum, oil and lubricants to be released into the ecosystem [15-17], causing devastation to its wildlife.

About the Authors

Laura is a PhD student at Royal Holloway University of London interested in decadal climate variability and policy. She has been working as a website assistant for the AntarcticGlaciers.org team for a year leading the ESRI StoryMap Collections and has written a series of introductory articles for the website.

Benjamin is a recent geography graduate from Royal Holloway University of London. He will be starting his postgraduate degree in ‘Holocene Climates’ at the University of Cambridge. Benjamin’s interests lie in understanding the environmental response and interactions between physical and human systems.


[1] Verbitsky, J. (2018) ‘Ecosystem services and Antarctica: the time has come?’, Ecosystem Services, 29(B), pp. 381-394.

[2] Verbitsky, J. (2013) ‘Antarctic tourism management and regulation: The need for change’, Polar Record, 49(3), pp. 278-285.

[3] Bender, N. A., Crosbie, K. and Lynch, H. J. (2016) ‘Patterns of tourism in the Antarctic Peninsula region: A 20-year analysis’, Antarctic Science, 28(3), pp. 194–203.

[4] Bastmeijer, Kees, Lamers, M. and Harcha, J. (2008) ‘Permanent land-based facilities for tourism in Antarctica: The need for regulation’, RECIEL, 17(1), pp. 84-99.

[5] Weber, M. (2012) ‘Cooperation of the Antarctic Treaty System with the International Maritime Organization and the International Association of Antarctica Tour Operators’, The Polar Journal, 2(2), pp. 372-390.

[6] O’Neill, T. A. (2017) ‘Protection of Antarctic soil environments: A review of the current issues and future challenges for the Environmental Protocol’, Environmental Science & Policy, Volume 76, pp. 153-164.

[7] Stonehouse, B. (1992) ‘IAATO: An association of Antarctic tour operators’, Polar Record, 28(167), pp. 322-324.

[8] Pfeiffer, S. and Peter, H.-U. (2004) ‘Ecological studies toward the management of an Antarctic tourist landing site (Penguin Island, South Shetland Islands)’, Polar Record, 40(4), pp. 345-353.

[9] Abdullah, N. C. and Shah, R. M. (2018) ‘Guidelines for Antarctic tourism: An evaluation’, Environment Behaviour Proceedings Journal, 3(7), pp. 1-6.

[10] Pfeiffer, S. and Peter, H-U. (2004) ‘Ecological studies towards the management of an Antarctic tourist landing site (Penguin Island, South Shetland Islands)’. Polar Record. 40(4). PP. 345-353

[11] Curry, C. H., McCarthy, J. S., Darragh, H. M., Wake, R. A., Todhunter, R. and Terris, J. (2002) ‘Could tourist boots act as vectors for disease transmission in Antarctica?’, Journal of Travel Medicine, 9(4), pp. 190–193.

[12] Chown, S. L., Huiskes, A. H. L., Gremmen, N. J. M., Lee, J. E., Terauds, A., Crosbie, K., Frenot, Y., Hughes, K. A., Imura, S., Kiefer, K., Lebouvier, M., Raymond, B., Tsujimoto, M., Ware, C., Van de Vijver, V. and Bergstrom, D. M. (2012) ‘Continent-wide risk assessment for the establishment of nonindigenous species in Antarctica’, Proceedings of the National Academy of Sciences of the United States of America, 109(13), pp. 4938-4943.

[13] Kessely, B. (2007) Report of investigation in the matter of sinking of passenger vessel EXPLORER (O.N. 8495) 23 November 2007 in the Bransfield Strait near the South Shetland Islands [Online]. Available at: http://www.cruisejunkie.com/Explorer%20-%20Final%20Report.pdf (Accessed: 23 August 2021).

[14] Brosnan, I. G. (2011) ‘The diminishing age gap between polar cruisers and their ships: A new reason to codify the IMO Guidelines for ships operating in polar waters and make them mandatory?’, Marine Policy, 35(2), pp. 261-265.

[15] Ruoppolo, V., Woehler, E. J., Morgan, K. and Clumpner, C. J. (2013) ‘Wildlife and oil in the Antarctic: A recipe for cold disaster’, Polar Record, 49(2), pp. 97-109.

Ellipsoidal Basins

Ellipsoidal Basins is a geographical term used to describe deep, elongated lakes, formed by subglacial activity beneath past ice sheets [1]. Examples of these basins include the Great Lakes and Finger Lakes of North America [1,2]. These basins were formed either where the ice was topographically constrained (Finger Lakes), had vulnerable, softer, geology (the Great Lakes), or in an area of maximum ice discharge (Hudson Bay) [1].

All five of North America’s Great Lakes are pictured in this spectacular image captured by the Copernicus Sentinel-3 mission: Lake Superior, Michigan, Huron, Erie, and Ontario. From: ESA

All these ellipsoidal basins are orientated in the direction of past ice flow and near the ice sheet margin [3]. They have smoothed edges, which is typical of glacial landforms. A more commonly used term to describe this type of lake is glacial overdeepening.

Glacial overdeepenings are large-scale erosional landforms which have been widened and deepened to depths deeper than the pre-glacial valley [4]. Overdeepened basins can be also used to describe other glacial features such as cirques or fjord floors [3,5]. However, here we will be discussing overdeepened basins formed beneath ice sheets (ellipsoidal basins).

Finger Lakes of New York
Satellite Image of the Finger Lakes of New York, an example of ellipsoidal basins. Wiki Commons

Formation of Ellipsoidal Basins

Over the Quaternary Period (the last 2.6 million years), successive cold glacial periods allowed large ice sheets to spread over much of the high latitudes of the Northern Hemisphere, including the Laurentide Ice sheet [4] in North America. The Laurentide Ice Sheet expanded over Canada and some of the United States and was responsible for large glacial landforms seen today in these regions, including ellipsoidal lakes.

Our true understanding of the formation of ellipsoidal basins/ overdeepenings is incomplete because the area beneath active ice sheets is not accessible. However, signs of past glacial activity from glacial landforms within these basins reveals some of the processes involved in their formation [1].

Pre-glacial river valleys act as suitable channels for ice to flow through and become topographically constrained by the valley walls [3,6]. This constraint on the ice allowed overdeepening to occur, concentrating erosion to the base of the ice. The erosional processes acting beneath the ice are typically plucking, quarrying, scouring and abrasion and are all modulated by the thermal regime and the geology [3,6].

Case Study: The Great Lakes of North America

Both The Finger Lakes and the Great Lakes in North America are a classic example of ellipsoidal basins as they are a series of deep, elongated lakes arranged in an hierarchical structure [1]. The Great Lakes are the deepest and largest lakes in North America. Each lake basin originated as a northwardly flowing river, and over successive glaciations during the Quaternary period, was eroded into the present formations.

Satellite image of the Great Lakes, April 24, 2000. From Wikimedia. The Finger Lakes can be seen, just southeast of Lake Ontario.

Click on the map below to take you to an interactive map showing the flowlines of the Laurentide Ice Sheet, the ice sheet extent, and the Great Lakes. Can you also find the Finger Lakes in New York?

ESRI Interactive map showing the reconstructed Laurentide Ice Sheet extent [7], The Great Lakes and Flowlines [8]. Map created by Dr Bethan Davies.
  • The main layers in the map are the ice sheet margins, the directions of ice flow, and the Great Lakes.
  • Notice how the lakes extend in the direction of the ice flow, and are positioned near the ice sheet margin. Both of these characteristics are typical of glacial overdeepenings [3].
  • Try and locate the Finger Lakes in New York. What do they suggest about the direction of ice flow? Has it changed?
  • What do you notice about the margins of the Great Lakes? How do they compare to lakes in non-glaciated areas? Can you find an example of a non-glaciated lake (south of the limits of the Laurentide Ice Sheet) in North America for comparison – how are the margins and overall morphology different?

Case study: The Finger Lakes of North America

Shortly after 14,500 years ago, during the deglaciation of North America and the retreat of the Laurentide Ice Sheet, the 80 km wide Seneca-Cayuga paleo ice stream occupied the overdeepened New York State Finger Lake basins [9]. This ice stream formed mega-scale glacial lineations and other streamlined landforms.

Sookhan et al. 2021 (Figure 1). Lidar topography of f Finger Lakes region of Upper New York State, USA and contiguous parts of Ontario north of Lake Ontario.

The maps showed clear ice flow patters, with landforms representing faster flow (Mega Scale Glacial Lineations) to steady state flow (drumlins), and highlighted the role that the Finger Lakes had on the ice flow speed. Evidence also suggests that the fast ice flow resulted in the increase in erosion potential from abrasion and subglacial meltwater resulting in the continuous overdeepening of the Finger Lakes, causing them to have their deep, elongated structure [9].

Explore the Finger Lakes of New York in the interactive embedded Google Map below.

The Finger Lakes are around 200 m deep, and are cut into the Allegheny Plateau. They occupy narrow, steep-sided bedrock basins, extending up to 70 km into the plateau. The largest Finger Lakes radiate outward to the south, like fingers on an outstretched hand [9]. The bedrock floors of the largest lakes are over-deepened, to well below sea level (e.g. the Rochester Basin at – 244 m below mean sea level). This over deepening indicates that these lakes have been a locus for enhanced glacial erosion over multiple glacial cycles [9].

Drumlins and mega-scale glacial lineations are well aligned with the lakes, indicating the direction of ice flow.

Sookhan et al., 2021 (Figure 5). Geomorphological map of the study region.

We can use the orientation of these geomorphological features and the lakes, and the position of the moraines, to reconstruct the former ice-flow pathways of the Seneca-Cayuga paleo ice stream [9].

Sookhan et al., 2021, Figure 10. Map showing the footprints of the different paths of the palaeo ice stream.

Further reading

Earth from Space: the Great Lakes

Dig the Dunes: glaciation and the formation of Lake Michigan

Origins of the Great Lakes

Life in the Finger Lakes

Open access images used were available under a Creative Commons License.


1. White, W.A. (1972) Deep erosion by continental ice sheets. Geoological Society of North America. 83. 1037-1056.

2. Sugden, D.E. (1972) A case against deep erosion of shields by ice sheets. Geology. 4. 580-582

3. Patton, H., Swift, D.A., Clark, C.D., Livingstone, S.J., Cook, S.J. (2016) Distribution and characteristics of overdeepenings beneath the Greenland and Antarctic ice sheets: Implications for overdeepening origin and evolution. QSR. 148. 128-145.

4. Cook, S., and Swift, D.A. (2012) Subglacial basins: Their origin and importance in glacial systems and landscapes. Earth Science Reviews. 115. 332-372.

5. Burschil, T., Tanner, D.C., Reitner, J.M., Buness, H., and Gabriel, G. (2019) Unravelling the shape and stratigraphy of a glacially-overdeepened valley with reflection seismic: the Leinz Basin (Austria). Swiss Journal of Geosciences. 112. 341-355

6. Benn, D.I., and Evans, D.J.A., 2010. Glaciers and Glaciation. Hodder-Arnold, London

7, Dalton, A.S. et al. (2020) An updated radiocarbon-based ice margin chronology for the last deglaciation of the North American Ice Sheet Complex. Quaternary Science Reviews. 234. 106223.

8. Marigold, M., Stokes, C.R., Clark, C.D., and Kleman, J. (2015) Ice streams in the Laurentide Ice Sheet: a mew mapping inventory. Journal of Maps. 11(3). 380-395.

9. Sookhan, S., Eyles, N., Bukhari, S. & Paulen, R. C. LiDAR-based quantitative assessment of drumlin to mega-scale glacial lineation continuums and flow of the paleo Seneca-Cayuga paleo-ice stream. Quat. Sci. Rev. 263, 107003 (2021). https://www.sciencedirect.com/science/article/pii/S0277379121002109


Trimlines are erosional features which mark the maximum vertical extent of a past glaciation [1].

Different types of trimlines exist, dependent on the length of time since the last glacial advance [2]. In recently glaciated valleys, they are marked by a distinct change in vegetation. Above the trimline, dense vegetation exists with species characteristic of the region[2,3]. And below the trimline, valley sides are characteristic of bare, ice-scoured rock, or with early stages of vegetational development [2,3]. These are termed ‘Vegetational Trimlines‘, and are commonly associated with glacial activity since the Little Ice Age, within the historical era [2,3].

For older glaciations, occurring prior to the Little Ice Age, the vegetation change may be less distinctive as vegetation succession has occurred [2,4]. Therefore, these trimlines mark the boundary between the smooth, ice-scoured bedrock below the trimline, and the frost-shattered regolith from periglacial weathering above [3]. These can be termed ‘Peri-glacial Trimlines’ [2,3,5].

Image of the Callequeo Glacier and its terminal lake with trimlines visible from past glacial advance.
Valley side trimlines (labelled with white arrows) marking the former thickness of the Callequeo Glacier, Monte San Lorenzo. Photo credit: J. Martin.

What are Trimlines Used For?

Unlike other glacial landforms which show the lateral extent, or behaviour of a past glaciations, trimlines mark the maximum vertical extent of the ice surface [3,4]. This enables the production of 3-D model reconstructions of ice sheets and valley glaciers[4,6].

In currently occupied glacial regions, trimlines can be compared to the modern ice surface elevation to assess the role of ice surface thinning, and responses to climate change [7].


[1] McCarroll D. (2014) Trimline. In: Encyclopedia of Planetary Landforms. Springer, New York, NY. doi.org/10.1007/978-1-4614-9213-9_383-1

[2] Benn, D.I., and Evans, D.J.A., 2010. Glaciers and Glaciation. Hodder-Arnold, London

[3] Rootes, C.M., and Clark, C.D. (2020) Glacial trimlines to identify former ice margins and subglacial thermal boundaries: A review and classification scheme for trimline expression. Earth-Science Reviews. 210. 103355.

[4] McCarroll, D. (2016) Trimline Trauma: The wider implications of a paradigm shift in recognising and interpreting glacial limits. Scottish Geographical Journal. 132(2).

[5] Ballantyne, C. K. (1997). Periglacial Trimline in the Scottish Highlands. Quaternary
International, 38, 119–136.

[6] Ballantyne, C. K. (2010). Extent and Deglacial Chronology of the Last British‐Irish Ice Sheet: Implications of Exposure Dating Using Cosmogenic Isotopes. Journal of Quaternary Science, 25(4), 515–534.

[7] Kohler, J., James, T., Murray, T., Nuth, C., Brandt, O., Barrand, N., Aas, H. & Luckman, A.
(2007). Acceleration in Thinning Rate on Western Svalbard Glaciers. Geophysical Research
Letters, 34(18).


What are flutes?

Glacial flutes are elongated, low-relief ridges formed subglacially and orientated in the direction of glacier flow [1,2,3]. Their size can range between several centimetres to a few metres both wide and high, and occur in groups of streamlined ridges known as ‘swarms’ [1].

Flutes are formed subglacially and are found in glacial foregrounds. They are more likely to be found in modern glacier foreground as they can be subjected to erosion because of their till-like composition [1].  

Fluted surface in the Brúarjökull foreground 2004. Source: Ólafur Ingólfsson

Flutes are found in a variety of glaciated regions including Iceland, Sweden, Norway, New Zealand, and Alaska [1,2,3]. Because of their relatively small size, they are often hard to identify whilst at ground level. Therefore high-resolution satellite data or LiDAR methods are used to map them [2].

Flute formation

Flutes can be formed subglacially beneath both polythermal, and warm-based glaciers. There have been several models proposed about the formation of flutes, but the most widely accepted model is the Cavity Infill Model [1,2,4].

This model proposes that a boulder causes an obstruction beneath the actively flowing glacier. The glacier then forces highly saturated sediment into a cavity on the leeside of the boulder obstruction [1,2]. The pressure on the leeside of the boulder drops, allowing the saturated sediment to freeze, and is carried forward by the ice, forming the elongated flute shape [1,3].


[1] Benn, D.I., and Evans, D.J.A., 2010. Glaciers and Glaciation. Hodder-Arnold, London

[2] Ely, J.C., Graham, C., Barr, J.D., Rea, B.R., Spagnolo, M., and Evans, J. (2016) Using UAV acquired photography and structure from motion techniques for studying glacier landforms: application to the glacial flutes at Isfallsglaciären. Earth Surface Processes and Landforms. DOI: 10.1002/esp.4044.

[3] Gordon, J.E., Whalley, W.B., Gellatly, A.F., Vere, D.M. (1992) The formation of glacial flutes: Assessment of models with evidence from Lyngsdalen, North Norway. QSR. 13(7). PP. 709-731.

[4] Boulton, G.S. (1976) The origin of glacially fluted surfaces – observations and theory. Journal of Glaciology. 17. PP. 287-309.

Tidewater Glaciers

What is a Tidewater Glacier?

Tidewater glaciers are glaciers which extend out, and terminate into the sea [1]. They are part of a group of glaciers known as calving glaciers, as their main method of ice loss is through iceberg calving, instead of surface melt [1,2]. Calving icebergs currently accounts for up to 70% of the worlds annual mass transfer from glacial regions to the ocean [1].

Whisky Glacier, a floating tidewater glacier in Whisky Bay, James Ross Island

Tidewater glaciers are found at latitudes of 45 and above, and are present in different glacial regions including Antarctica, Alaska, Greenland, Svalbard, and Patagonia [1,2].

Types of Tidewater Glacier

Mountain glaciers terminating into the ocean are called ‘tidewater glaciers’. ‘Tidewater outlet glaciers’ are glaciers which reach the ocean through fjords, branching off from ice caps, ice sheets or icefields [1].

Tidewater glaciers can either be grounded – where the glacier is in constant contact with the bed. Or they can be floating – when the terminus is floating on the sea water, or flowing into an ice shelf [1,3]. Grounded glaciers tend to be located in temperate regions such as Alaska, or Canada. And floating tidewater glaciers are commonly found in polar regions, namely Greenland, Svalbard, and Antarctica.

Tidewater Glaciers and Iceberg Calving

Calving icebergs are the most efficient method of losing mass from a glacier [4]. It is the dominant cause of mass loss from the Antarctic Ice Sheet [5], therefore, it is important to understand the process behind these calving events [1,4]

Iceberg calving occurs when there are faults in the glacier, known as crevasses. Crevasses can form when there stress and strain thresholds are reached on the glacier. The trigger for the iceberg calving events vary for both grounded and floating tidewater glaciers.

A tidewater glacier with crevasses calving icebergs

Floating tidewater glacier

For a floating tidewater glacier, submarine melting of the underside of the glacier causes a direct loss of ice, as well as undercutting the floating glacier terminus or ice shelf [6]. This causes instability, resulting in complete collapse [1,6].

When the floating section of the tidewater is removed, the ice on the land is no longer supported from the buttressing ice shelf. It is then able to rapidly, and continuously calve icebergs. For example, the Larsen B ice shelf collapse in 2002 on the Antarctic Peninsula [4].

Grounded tidewater glaciers

Grounded tidewater glaciers calve when there is either a rapid thinning of the glacier surface, or a localised change in sea level. This change forces the glacier terminus to be out of equilibrium with the ocean, resulting in the terminus to be lifted and detached from the bed, causing the terminus to become buoyant [6]. During this process, the crevasses are able to isolate large blocks of ice which are then calved into icebergs.

Illustration of a grounded glacier during a calving event.


[1] Vieli, A., 2011. Tidewater glaciers, in: Singh, V.P., Singh, P., Haritashya, U.K. (Eds.), Encyclopedia of Snow, Ice and Glaciers. Springer, pp. 1175–1179.

[2] Benn, D.I., Hulton, N.R.J., Mottram, R.H., 2007. “Calving laws”, “sliding laws” and the stability of tidewater glaciers, in: Sharp, M. (Ed.), Annals of Glaciology, Vol 46, 2007, Annals of Glaciology. Int Glaciological Soc, Univ Ctr Svalbard UNIS, NO-9171 Longyearbyen, Norway. Benn, DI, Univ Ctr Svalbard UNIS, Box 156, NO-9171 Longyearbyen, Norway., pp. 123–130.

[3] van der Veen, C.J., 2002. Calving glaciers. Prog. Phys. Geogr. 26, 96–122. https://doi.org/10.1191/0309133302pp327ra

[4] Benn, D.I., and Evans, D.J.A., 2010. Glaciers and Glaciation. Hodder-Arnold, London

[5] Shepherd, A., Ivins, E., Rignot, E., Smith, B., Van Den Broeke, M., Velicogna, I., Whitehouse, P., Briggs, K., Joughin, I., Krinner, G., IMBIE Team, 2018. Mass balance of the Antarctic Ice Sheet from 1992 to 2017. Nature 558, 219–222. https://doi.org/10.1038/s41586-018-0179-y

[6] Benn, D.I., Astrom, J., Zwinger, T., Todd, J., Nick, F.M., Cook, S., Hulton, N.R., and Luckman, A. (2017) Melt under-cutting and buoyancy-driven calving from tidewater glaciers: new insights from discrete element and continuum model simulations. Journal of Glaciology. 63(240).

Younger Dryas glacial moraines (Lake District)

By Dr Richard Waller, Keele University, and Dr Bethan Davies, Royal Holloway University of London

During the Younger Dryas, the Lake District was covered by plateau icefields and cirque glaciers[1]. The image below shows the larger plateau icefields (green) and the smaller cirque glaciers (red) in the Lake District and Snowdonia.

Ice masses in Wales and the Lake District. From Bickerdike et al., 2018

You can explore all of the locations in this page using the Younger Dryas Glacial Map. This version of the map is focused on the Lake District.

Younger Dryas Glacial Map – Lake District

Greenup Gill

These ice masses left behind numerous moraines as they retreated. The image below (credit Dr Richard Waller) shows some 360º imagery of a fabulous set of hummocky moraines in Greenup Gill, near Borrowdale, in the Central Lake District[3]. These glacial landforms show the retreat of a small plateau icefield outlet glacier during the Loch Lomond Stadial[1,3].

The moraines show the retreat of the glacier all the way up onto the plateau, showing the active retreat of this plateau icefield. The continuous moraine sequences shows that the outlet glacier retreated towards its plateau source area without becoming disconnected from the plateau icefield accumulation area[2].

You can see the mapped moraines of this icefield for yourself in the Younger Dryas Glacial Map.

Greenup Gill moraines (dark grey) and the plateau icefield (light gray) from the plateau icefield, Younger Dryas Glacial Map.


This 360º image shows a lateral moraine (a moraine formed at the sides of the glacier) in Bannerdale (credit Dr Richard Waller). Bannerdale held a small cirque glacier during the Younger Dryas, with lateral moraines demarcating the glacier limits.

In the image below, the lateral moraine is visible as a linear mound of sediment against the valley side walls, in the immediate foreground. Some glacially transported boulders are visible on the ridge of the moraine.

Bannerdale, just to the east of Blencathra, held small cirque glaciers during the Younger Dryas. The orange in this map is mapped as ‘hummocky moraine’ by Sissons (1980).


Haweswater also held a plateau icefield during the Younger Dryas [1,3].

Younger Dryas Glacier Map, showing plateau icefield above Haweswater.

This is a set of moraines above Haweswater (credit Dr Richard Waller). The moraines track the recession of the plateau icefield outlet glaciers onto the upland areas [5].

You can explore these moraines yourself in Google Earth or in the Younger Dryas Glacial Map. The moraines are visible in the satellite imagery as rounded hummocks with scattered boulders.

The Younger Dryas Glacial Map shows the locations of these moraines, just at the head of Haweswater Reservoir.

Younger Dryas moraines at the head of Haweswater Reservoir


Gillercomb, the valley just to the west of Seathwaite (Cumbria), preserves a number of glacier moraines deposited during the Younger Dryas.

Gillercomb, west of Seathwiate

The location can be explored in Google Maps. The moraines are visible as the smoothed, elongated mounds in the valley floor.

These moraines were formed during the recession of the plateau icefield that covered this part of Cumbria during the Younger Dryas [6].

Gillercomb, west of Seathwaite in Cumbria. Younger Dryas Glacial Map.

Grains Gill

A number of small elongate moraines exist in the bottom of the Derwent river valley, just south of Seathwaite. These moraines have a number of glacially transported boulders on their summits.

Screenshot from the Younger Dryas Glacial Map of Grains Gill moraines.

Here is the location of the mapped geomorphology:

Further reading


1. Bickerdike, H. L., Ó Cofaigh, C., Evans, D. J. A. & Stokes, C. R. Boreas 47, 202–224 (2018).

2. Boston, C. M. & Lukas, S. J. Quat. Sci. 34, 433–451 (2019).

3. McDougall, D. A. J. Quat. Sci. Publ. Quat. Res. Assoc. 16, 531–543 (2001).

4. Sissons, J. B. Earth Environ. Sci. Trans. R. Soc. Edinburgh 71, 13–27 (1980).

5. McDougall, D. Quat. Sci. Rev. 73, 48–58 (2013).

6. McDougall, D. A. (1998). Loch Lomond stadial plateau icefields in the Lake District, northwest England. PhD thesis, University of Glasgow.

Alpine icefield landsystem of upland Britain

This article was written by Dr Hannah Bickerdike.

The Loch Lomond Stadial in Britain

Between 12,900 and 11,700 years ago, gradual warming of Britain’s climate was interrupted by a sudden period of renewed cooling. During this period, known as the Loch Lomond or Younger Dryas Stadial, glaciers regrew in many areas of upland Britain.

Evidence of these glaciers is preserved in a range of different glacial landsystems in Britain. Even though these glaciers have long since disappeared, by studying the Younger Dryas glacial landsystems they left behind, we can understand what processes operated in these glacial environments.

Glacial geomorphology in Scotland dating from the Younger Dryas. Credit: Bickerdike et al., 2018

The alpine icefield landsystem

The most widespread landsystem of the Loch Lomond Stadial is the alpine icefield, evidence of which is found throughout the mountainous areas of the Western Grampian Highlands of Scotland and on several of the Western Isles, including Skye and Mull.

This landsystem is a type of glaciated valley landsystem, usually consisting of a series of steep-sided, glacial valleys, separated by arêtes and spurs. The size and shape of these glaciers was strongly controlled by the topography, with ice confined to within the valleys.

In some places, ice from two or more separate valleys would join together over lower sections of the mountain ridges, called cols. This created networks of connected valley glaciers called icefields.

Conceptual diagram of the alpine icefield landsystem. Glacier size, shape and flow was largely controlled by topography. Adapted from Bickerdike et al., 2018 – https://onlinelibrary.wiley.com/doi/full/10.1111/bor.12259  

Landforms of the alpine icefield landsystem

The diagram below shows the types of landform usually found in the Loch Lomond Stadial alpine icefield landsystem in Britain. The numbered features are discussed below.

Glacial geomorphology of the alpine icefield landsystem. Adapted from Bickerdike et al., 2018 -https://onlinelibrary.wiley.com/doi/full/10.1111/bor.12259

#1. Recessional moraines

The most widespread feature of this landsystem is sequences of recessional moraines, which are arranged in concentric ridges on the valley floors and lower slopes. Moraines are piles of debris, usually mud, sand, and boulders, all deposited in piles at the ice terminus. They are typically unsorted and chaotic.

These moraines formed during short phases of glacier advance and retreat that interrupted the general pattern of glacier retreat and are typical of active temperate glaciers.

Recessional hummocky moraines in Strath Beag, Isle of Skye. Source Bickerdike et al., 2018 – https://onlinelibrary.wiley.com/doi/full/10.1002/jqs.3010

#2. Moraine mounds

Sometimes there are small patches of more chaotically arranged moraine mounds (2) within these sequences. Areas of extensive moraines indicate that the Loch Lomond Stadial glaciers transported large volumes of debris.

Some of this debris likely fell onto the glacier surfaces from the surrounding valley slopes but it is also thought that the glaciers reworked large volumes of debris that was already present in the landscape.

#3. Eskers

In some places, eskers (3) are present on the valley floors, but these are less common. Eskers are ridges of sand and gravel, deposited by glacial meltwater flowing through tunnels within and underneath glaciers. After the glacier disappears, these sediments are left behind as a ridge in the landscape.

A recently formed Esker – sinuous tidge aligned more or less along ice flow. Credit: Frances Butcher

#4. Medial moraines

Similarly, medial moraines (4) may mark locations at the confluence of two valley glaciers, but evidence of these within this landsystem is rare. Medial moraines form where two glaciers met.

#5. Terminal moraines

In some valleys, particularly those with cirques at their heads, recessional moraines are only found in the area around the former glacier terminus (5).

#6. Flutes

In these valleys with cirques at their head, the upper valley might be covered within a thin blanket of till or show evidence of flutes (6). Flutes are streamlined ridges of sediment, sometimes with a boulder or obstacle at their head, that formed subglacially underneath temperate ice.

#7, #8. Erosional landforms

At the heads of these valleys, erosional glacial landforms can often be found. These can include roches moutonées (7), formed by abrasion and quarrying of the bedrock under the sliding glacier, and ice-smoothed bedrock (8).

Roche moutonnée from Scotland, with a gently sloping stoss face and a blunt lee face. Photo: David Baird

#9. Trimlines

In many areas, the height of the former glacier surface is marked by trimlines (9). These features show the height of the former glacier surface on the valley slopes.

Trimlines can be identified by the contrast between glacial landforms below the trimline (in the area covered by the former glacier), and evidence of frost-shattering and periglacial processes above the trimline (in areas that remained above the glacier surface).

Cast study: Isle of Mull Alpine Icefield

The Isle of Mull on the West coast of Scotland shows glacial geomorphology typical of the alpine icefield landsystem. The numbers on the map match with the features described above.

The Isle of Mull had an independent ice domes that deflected mainland ice around it during the Last Glacial Maximum. During the Younger Dryas, it was glaciated with an independent mountain icefield.

Ice drained from the broad uplands of Sgurr Dearg and the Beinn Talaidh-Corra-bheinn ridge to form the Ba and Forsa outlet glaciers to the northwest and north, respectively.

The lower slopes of these valleys are covered with nested lateral moraines, chains of recessional moraines and thick drift of glacial sediments. The terminus of the glaciers is obscured by glaciofluvial outwash sands and gravels.

Example of the Loch Lomond Stadial alpine icefield landsystem on the Isle of Mull, Scotland (originally mapped by Ballantyne 2002). Underlying hill‐shaded images were derived from NEXTMap DSM from Intermap Technologies, Inc. provided by the NERC Earth Observation Data Centre. Adapted from Bickerdike et al., 2018 – https://onlinelibrary.wiley.com/doi/full/10.1111/bor.12259

There were six cirque glaciers around the margins of the icefield. They were not connected to the main icefield.

In summary, the Loch Lomond Stadial alpine icefield landsystem is found in upland areas of Britain with interconnected steep-sided glacial valleys.

The landsystem contains: sequences of recessional moraines on the valley floors and lower slopes (typical of active temperate glaciers); flutings or glacial erosional landforms in the upper valleys; and trimlines marking the former glacier surface.


You can explore the glacial landforms of Mull using the Younger Dryas Glacial Map.

Use the map to zoom to the Isle of Mull. Zoom in and out and explore the landforms. Turn the basemap to satellite imagery and investigate the geomorphological evidence for yourself. Can you see the features in the satellite imagery?

The Younger Dryas Glacial Map

Further reading

About the Author

Hannah Bickerdike completed her BSc in Geography at the University of St Andrews. She subsequently undertook a PhD at Durham University, studying the geomorphology of the Loch Lomond/Younger Dryas Stadial glaciers of Britain. A key element of this work was compiling geomorphological evidence of these glaciers, mapped in previous research, into a GIS database of over 95,000 features, a version of which can be found on this site.


  1. Bickerdike, H. L., Ó Cofaigh, C., Evans, D. J. A. & Stokes, C. R. Boreas 47, 202–224 (2018).
  2. Bickerdike, H. L., Evans, D. J. A., Stokes, C. R. & Ó Cofaigh, C. J. Quat. Sci. 33, 1–54 (2018).
  3. Bickerdike, H. L., Evans, D. J. A., Ó Cofaigh, C. & Stokes, C. R. J. Maps 12, 1178–1186 (2016).

From Snow to Firn to Glacier ice


How do we build a glacier? We start with a snowflake. Snow, over time, is compressed into firn, and then into glacier ice.

Snow falls in cold regions, such as mountain tops or in polar regions. In glaciology, snow refers to material that has not changed since it fell1.

Snow is very light and fluffy, and has a very low density. If the snow is wetter, it will have an increased density. Snowflakes have a hexagonal structure, and fallen snow has a significant amount of air in it.

Snow flakes by Wilson Bentley. Bentley was a bachelor farmer whose hobby was photographing snow flakes. ; Image ID: wea02087, Historic NWS Collection ; Location: Jericho, Vermont ; Photo Date: 1902 Winter. From Wikimedia Commons


Firn is usually defined as snow that is at least one year old and has therefore survived one melt season, without being transformed to glacier ice.

Firn is transformed gradually to glacier ice as density increases with depth, as older snow is buried by newer snow falling on top of it. Year after year, successive accumulation layers are built up. In the accumulation zone of a glacier, density therefore increases with depth; the rate depends on the local climate and rate of accumulation1. Firn transforms to glacier ice at a density of 830 kg m-3.

New snow (immediately after falling, calm conditions50-70
Damp new snow100-200
Settled snow200-300
Wind-packed snow350-400
Very wet snow and firn700-800
Glacier ice830-923
Typical densities (kg m-3). From Cuffey and Paterson, 2010.
A scientist collecting snow and ice samples from the wall of a snow pit. Fresh snow can be seen at the surface and en:glacier ice at the bottom of the pit wall. The snow layers are composed of progressively denser en:firn. Taku Glacier, Juneau Icefield, en:Tongass National Forest, en:Alaska. From Wikimedia Commons

Firn transforms to glacier ice in 3-5 years in the temperate Upper Seward Glacier in the St Elias Mountains near the Alaska-Yukon border. Firn becomes ice at a depth of about 13 m1. At sites like this with rapid snow accumulation, the depth of a firn layer, and the load on it, increases rapidly with depth.

However, in cold, dry East Antarctica, firn becomes ice at a depth of 64 m at Byrd and 95 m at Vostok. 280 years are needed at Byrd, and 2500 at Vostok. Low temperatures slow the transformation. Temperatures at Vostok, the coldest region of Earth, are 30°C lower than Byrd, which explains the slower increase in density. In addition, slow accumulation gives slow burial, and a small load each year; the increase in density takes much longer.

Typically, the transformation of firn to ice takes 100-300 years, and a depth of 50 – 80 m1.

Glacier ice

Firn becomes glacier ice when the interconnecting air or water-filled passageways between the grains are sealed off (“pore closure”)1. Air is isolated in separate bubbles. This occurs at a density of 830 kg m-3. The air space between particles is reduced, bonds form between them, and the particles grow larger. This is a process known as sintering. Increasing pressure compresses the bubbles, placing the enclosed air under pressure and increasing the density of the ice2.

Fresh snowflakes, which have a complex shape, have a large surface area. Over time and under pressure, the surface area is reduced, the surface is smoothed, and the total surface area is reduced. Fresh, complex snowflakes are transformed into rounded particles.

Formation of glacier ice. Luis Maria Benitez, Wikimedia Commons

The transformation of firn to ice is much faster where there is melting and refreezing2.  Meltwater can percolate downwards, infilling porespaces, and the displaced air escapes upwards. If the snow is under 0°C, the water will freeze, producing areas of compact ice.  This will produce high density ice much more rapidly than in colder regions without melting.

The density of pure glacier ice is usually taken as 917 kg m-3. This strictly is only true at 0°C and in the upper layers of ice sheets and mountain glaciers; the density may be greater at the mid-depth ranges in polar ice sheets, where there are no bubbles and temperatures are -20°C to -40°C1.

Below 4 km of ice, such as at the centre of the East Antarctic Ice Sheet, the pressure would increase the density to 921 kg m-3.


Bubbles are common in glacier ice. Bubbles can contain liquid water or atmospheric gases, making them very useful for ice core research. The air in the bubble largely reflects the atmospheric concentrations when the ice formed1. In polar environments, bubbles in the ice occupy about 10% of the volume when firn turns to ice.

Glacier ice with many bubbles exposed on the ice shelf. It is melting and thinning rapidly.
Close up of white bubble-rich ice. Note the sharp junction between the coarse-clear ice and bubble-rich ice.

With greater depth in polar ice sheets, bubbles shrink as the overlying ice increases. The gas pressure within the bubbles therefore increases, and at certain depths, the gas attains a dissociation pressure. The bubbles begin to disappear as the gas molecules form clathrate hydrates1.  This process takes thousands of years.


Glacier ice contains various impurities in tiny amounts. By most scales, glacier ice is a very pure solid-earth material, because the processes leading to snowfall on a glacier – evaporation, condensation, precipitation – act as a natural distillation system1.

However, glaciers can contain impurities. The dirtiest glaciers are mountain glaciers, where debris can fall directly onto the ice surface. On ice sheets and glaciers, dust and other debris may blow onto the ice surface.

Iceberg laden with debris from a glacier, Antarctic Peninsula

Debris on the ice surface can affect the absorption of energy at the ice surface, and lead to increased or decreased melting.

Supraglacial debris on Unnamed Glacier, James Ross Island, Antarctic Peninsula

Layers in the ice

Glaciers are composed of sedimentary layers in their accumulation zones, formed of annual layers of snowfall. These layers are initially parallel to the glacier surface. This is the primary stratification in structural glaciology.

In temperate and subpolar settings, the annual sedimentary layers consist of alternating thick layers of bubble-rich ice, which originated as winter snow, and thin layers of clear ice, which are the refrozen meltwater from the summer melt season.

Glacier ice exposed in an ice-cored moraine. Note the foliation with coarse clear ice and white bubble-rich ice.
Primary stratification on a glacier on James Ross Island, Antarctic Peninsula.

Debris horizons may form, when summer melting concentrates debris (such as rockfall and wind-blown dust) on the ice surface.

In cold polar regions, annual layering forms instead by seasonal variation of snow metamorphism and wind deposition1.

This 19 cm long of GISP2 ice core from 1855 m depth shows annual layers in the ice. This section contains 11 annual layers with summer layers (arrowed) sandwiched between darker winter layers. From the US National Oceanic and Atmospheric Administration, Wikimedia Commons.

Blue glacier ice

Glacier ice is blue because the longer visible wavelengths are absorbed. The more energetic, blue, wavelengths are scattered back2.  The effect is greatest with deep, basal ice, which is bubble free and has large crystals. The blue colour tends therefore to be most intense in the calls of calved icebergs or fresh fractures.

Rough, weathered ice and fresh snow will appear white because preferential absorption does not occur.

This iceberg is formed from basal glacier ice. It is blue an has basal dirt. Differential melting forms holes all over its surface.

Further reading


1.           Cuffey, K. M. & Paterson, W. S. B. The Physics of Glaciers, 4th edition. (Academic Press, 2010).

2.           Benn, D. I. & Evans, D. J. A. Glaciers & Glaciation. (Hodder Education, 2010).

Glacial ArcGIS Stories

There are many ArcGIS Story Maps around. Some are better than others; some take too long to load or are not well thought through. But some are excellent.

Asia’s melting glaciers

This well made Storymap focuses on melting glaciers in High Mountain Asia, and the impact this will have on water resources.


Who owns Antarctica? Antarctic geopolitics

This excellent and well presented, professionally built StoryMap illustrates who owns Antarctica and introduces the Antarctic Treaty.

Territorial claims of Antarctica.

Glaciation: past, present and future

This great ESRI Storymap introduces glaciers in the present day and at the Last Glacial Maximum. It uses shapefiles from resources like GLIMS or the Randolph Glacier Inventory, and the Global LGM shapefiles from Ehlers and Gibbard. It’s well made and up to date. It also uses the BRITICE map to introduce glacial landforms across the British Isles and the LGM and Younger Dryas in Britain.

Glacier lake hazards in Alaska

This ArcGIS Story by the Alaska Climate Science Centre is better than most. It’s all about glacier hydrology and glacier lakes in Alaska. The videos and pictures are well made, and interspersed with explanatory figures.

Alaska Climate Science Centre ArcGIS Story Map

Disappearing Glaciers

A nice, well illustrated, introduction to glacier recession and mapping glacier change over recent decades.

Disappearing Glaciers Story Map

The recession of Glacier National Park Glaciers

This is a great introduction to using imagery to track and map glacier recession from 1966 to the present day.

Recession of Glacier National Park Glaciers

Glacial Landforms Story Map

This ESRI Story Map introduces a host of glacial landforms. It was a little slow to run for me, though.

Glacial Landforms Story Map

An Introduction to Sea Ice

A lovely storymap that introduces and illustrates sea ice, with illustrations of how it changes with the seasons at both poles.

ESRI StoryMap: An Introduction to Sea Ice

Mapping Mount Everest

This storymap, by Alex Tait from the National Geographic Society, tells us all about Mount Everest and how we map it, with some beautiful graphics.

Mapping Mount Everest

Glacial Landforms of Snowdonia

A straightforward storymap that highlights the glacial landforms in Snowdonia.

Snowdonia Story Map

Connecticut’s landscape is the story of glaciers

Learn about the glacial landforms of Connecticut.

Connecticut’s glacial landscape

The River Tees from Source to Mouth

More fluvial than glacial, but this is a very nice storymap that covers the River Tees. It is suitable for pre-16 as well as post-16 education.

Further reading