North American Arctic – icy beauty

Look at this. As an abstract pattern, it looks like something Gustav Klimt might paint.

But drill down into it in more detail and it changes into an uncomfortably close view of a reptiles skin.

All images in this post come from the North American Arctic – a place made beautiful and strange by ice. Conditions are so cold that the soil layers are almost permanently frozen. The rare occasions when it melts warps the ground in various distinctive ways.

Take the first image – the striking elongated light-blue lozenges are lakes. Lakes may form in the Arctic in areas called thermokarst. This a landscape full of hollows formed when patches of permafrost melt, causing hollows in the ground. These elongated examples are unusual. No-one knows for sure why these “oriented lakes” form, but they are often aligned with the prevailing wind, suggesting it has a role to play.

Here are some other examples, which seem to have edges with two sets of directions, making some of them look like badly-drawn hearts.

The lizard skin pattern above is known as “patterned ground” forms where soils regularly freeze and thaw. The periodic expansion of ice rearranges the soil and in the case of these polygons, wedges of ice may form in a regular pattern.

These processes occur in ‘peri-glacial’ environments. The term literally means “around glaciers” but it occurs over vast areas of the Arctic that are too near sea-level for glacial ice to build up. It can also occur at height in milder climates such as the Cairngorms in Britain or on top of African volcanoes (or even on Mars). During the colder parts of the current Ice Age, when large areas of the world were covered by ice sheets, the areas to the south of the ice were often peri-glacial. Ice-wedges and other peri-glacial features are relatively common in southern England where I live.

Pingoes are classic peri-glacial feature. In England these are round lakes formed when plugs of ice melted thousands of years ago as the climate warmed. In the Arctic they are 30-50m high hills with a core of ice – the name is Inuit for ‘small hill’. He is an example that is still a hills in Canada (note the patterned ground to its south).

These peri-glacial features are best seen near to rivers that flow into the Arctic. Further south, vast areas have very little soil, having been scraped clean by vast ice-sheets. One advantage of this, from my point of view, is that the geology is extremely well-exposed.

Here on Bathurst island in the Canadian Arctic, open folds in the some Devonian sediments are beautifully clear, complete with thickening of layers in the fold hinges.

These crazily-shaped islands in Hudson Bay are relics of folding deep within the earth. Imagine walking along those thin islands!

I’ll end with my favourite trace of ice in Canada.

The ghostly marks hiding under productive land in southern Canada were produced in a vast lake that formed as an ice-sheet melted. Ice-bergs floating in the shallow lake scraped along the lake-bed, leaving these ‘keel-marks’.

Categories: Glacial, Great Geology in Google earth, landscape

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