Moraine refers to any glacially formed accumulation of unconsolidated glacial debris (soil and rock) which can occur in currently glaciated and formerly glaciated regions, such as those areas acted upon by a past
ice age. This debris may have been
plucked off the valley floor as a
glacier advanced or fallen off the valley walls as a result of
frost wedging. Moraines may be composed of silt like
glacial flour to large boulders. The debris is typically sub-angular to rounded. Moraines may be on the glacier’s surface or deposited as piles or sheets of debris where the glacier has melted. Moraines may also occur when glacier or
iceberg transported rocks fall into the sea as the ice melts.
Lateral moraines are parallel ridges of debris deposited along the sides of a glacier. The unconsolidated debris is deposited on top of the glacier by frost shattering of the valley walls and from tributary streams flowing into the valley. The till is carried along the glacial margin until the glacier melts. Because lateral moraines are deposited on top of the glacier, they do not experience the postglacial erosion of the valley floor and therefore, as the glacier melts, lateral moraines are usually preserved as high ridges.
Lateral moraines stand high because they protect the ice under them from the elements, which causes it to melt or sublime less than the uncovered parts of the glacier. Multiple lateral moraines may develop as the glacier advances and retreats.
Ground moraines are till covered areas with irregular topography and no ridges often forming gently rolling hills or plains. It is accumulated under the ice by lodgement, but may also be deposited as the glacier retreats. The ground moraine is located between the two lateral moraines.
