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This is Cwm Llwch in The Brecon Beacons National Park.
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Now, whether we call it a cwm in Wales, a corrie in Scotland, or a cirque in France, it all refers to the bowl or the amphitheater-shaped hollow at the head of a glacial valley.
And this is where the glacier began.
During the last ice age, snow fell and accumulated, piling up in the hollow here, and it became compressed into ice.
Under its own weight, the ice slowly started creeping down the valley, at a rate of about one metre per day, carving out this armchair-shaped hollow in the mountain.
Now there's a big cwm here, but within it is a smaller cwm on the other side of the valley just behind me.
And this was created by a little glacier, right at the end of the last ice age.
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Within the hollow of this little cwm, water has accumulated creating a lake called Llyn Cwm Llwch, that was created by material or moraine, deposited by the glacier.
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And in glaciology, we call these little lakes corrie lakes or tarns.
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Thank you to Oldham Hulme Grammar School for helping to support this Time for Geography video.
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