
| Images obtained by scientists show features on the floor of the North Sea that correspond to the advance and retreat of a single huge ice sheet
Researchers have discovered landforms that were created by a single huge ice sheet 1 million years ago.
Scientists have discovered vast landforms deep beneath the North Sea that suggest the region was engulfed by a giant ice sheet by the middle of the last ice age. The landforms are buried under a thick layer of mud. The study is published in the journal Science Advances, Live Science reports.
The images show features on the floor of the North Sea that correspond to the advance and retreat of a single, massive ice sheet that existed 1 million years ago. The discovery contradicts theories that smaller ice sheets repeatedly expanded and contracted during that time. These theories were based on numerous depressions that were thought to be caused by the movement of glaciers. But it turns out that they were created by strong ocean currents.
Scientists say they have found compelling evidence of one large ice movement during this time period, but locations outside the current study area may still contain evidence of multiple smaller ice sheets.

The study authors used high-resolution sound wave data to uncover hidden terrain. They weren't looking for anything specific and were surprised to find evidence of a single ice sheet.
Such ice sheets move sedimentary rocks as they grow and shrink, creating erosional and sedimentary landforms that scientists can use to reconstruct the region's glacial past. When the ice advances, the scientists say, it creates elongated features that shape sedimentary rocks in the direction of the ice's movement. When the ice retreats, it creates features that show the clear boundaries of the ice sheet.
Scientists say the massive ice sheet formed during the last ice age, known as the Middle Pleistocene transition, which lasted from 1,3 million to 700 years ago. The ice age itself lasted from 000 million to about 2,6 years ago.

It was 1 million years ago that serious climate changes occurred on Earth, and the ice age periods themselves lasted longer and there was large-scale movement of ice, which is why scientists want to find out what happened then.
The new study doesn't yet answer where the ice spread during the Middle Pleistocene transition, but it could help scientists paint a picture of the conditions that led to global climate change.
The landforms revealed indicate that an ice sheet covered modern-day Norway and extended towards the British Isles. Some of the traces left by its retreat resemble a series of cracks and were formed when the ice sheet "sat" on the soft sediments just before it retreated. For thousands of years after the ice sheet retreated, the landforms were covered with mud and hidden.
The study provides clues about how ice sheets grow and break up during climate change.