What Happens to Landscapes That Were Glaciated?

Glaciers erode landscapes AND they deposit material.
Glacial landscapes have both erosional and depositional features.

On the right is Yosemite Valley National Park.  Spectacular granite walls.  In the vicinity of 20ky (20 thousand years) ago, Yosemite probably looked like this place in Alaska, on the right, the Ruth Gorge.  Indeed the highest portions of big cliffs (like El Capitan on the right) were not glaciated, just like the scene in the Ruth Gorge.

The cartoon image at right shows some key features of glaciated mountainous terrain.
Glaciers effectively slice into mountain sides forming steep ridges (aretes) and pointy summits (horns).
Cirques are bowl shaped regions at the head (or source region) of a glacier.
In the image, we see a trunk glacier (called “Valley Glacier”) fed by tributary glaciers.  Each glacier has a pile of debris on its sides, called lateral moraines, which consist of loose unconsolidated and poorly sorted and stratified glacial sediment (called till).  Where the tributary glaciers entre the trunk glacier, their lateral moraines become sediment piles within the trunk glacier and are then called medial moraines.

Here is a glacial valley– characterized by a U-shape, such that the floor of the valley is typically relatively flat, and the stream or river seems a bit small to have generated such a major feature.  Note the earlier picture of Yosemite Valley and its “flat floor.”

If glacial valleys contained exposed bedrock, the rock will often show glacial striae, like those on the right (formed by the glacier sliding over the rock).

On the left, loose unconsolidated and poorly sorted rock left behind by glacial activity– till, in a moraine.  And, on the right, an air-photo of recessional moraines cutting across a lake, representing various stages of terminal moraines during glacial retreat– Lake Granby, Colorado.

In summary,
moraines (a geomorphic feature), which consist of till (a kind of sediment) are depositional features;
whereas, cirques, aretes, horns, and U-shaped valleys are all erosional features.

Evolution of Glacial Landscapes

Glaciers create rather tell-tale landscape features.
The mountain peaks that have, or have had, glaciation tend to be pointy and rugged (horns and aretes!).
Even if a cirque glacier is largely gone and melted away, that eroded region will typically contain a glacier lake called a tarn.
Downstream from the tarn, one sometimes finds a string of lakes called paternoster lakes, which formed in small scoops downstream from the glacial cirque.  A trunk glacier will leave behind a U-shaped valley.
The following is an interesting animation, created by ….  which shows how a hypothetical landscape might change after a couple phases of glacial formation, advance, and retreat.