Home >> Science & Nature >> Rocks & Minerals

Types of Glacial Moraines

As glaciers plow across land and carve into valleys, they accumulate debris. During its lifetime and as the glacier melts, this debris is deposited as land formations known as moraines. Most are remnants of ancient glaciers from the Ice Age, though present-day glaciers have moraines as well. Moraines consist mainly of debris called glacial till, which are unsorted and unstratified collections of gravel, soil, clay and boulders of various sizes The type of moraine that forms is determined by the location of the debris in the glacier and the glacier's development over time.

Ground Moraine
- A ground moraine is a flat deposit of till on a valley floor that is left after a glacier retreats. A ground moraine can also form from flowing meltwater during ablation, when the glacier melts.
Lateral Moraine
- Lateral moraines describe accumulations of till that form in ridges at the edge of glaciers or are left behind at the edge of formerly glaciated valleys. They are formed mainly from rocks that broke from the valley walls and were carried at the edge of the glacier before being deposited.
Medial Moraine
- Medial moraines form from the lateral moraines of two glaciers that collided and merged into one. They appear as a center ridge of debris along the middle of a glacier or formerly glaciated valley.
End and Terminal Moraines
- An end moraine is a ridge or mound of material that forms at the perimeter of an actively flowing glacier. A terminal moraine is a type of end moraine that marks the glacier's furthest reaches, often forming as a large mound.
Recessional Moraine
- Similar to a terminal moraine, a recessional moraine is a large mound of debris formed during a period when the glacier is stationary for a significant period of time.
Push or Thrust Moraine
- Push or thrust moraines are formations created during temporary periods of warmth followed by return to a colder climate. A glacier begins to retreat, leaving till, but then returns with the temperature drop, and then bulldozes the debris it had previously deposited. As a result, push moraines have notably horizontal debris pointing up in the air.
Hummocky and Kame Moraines
- Hummocky moraines are irregular formations with a knot-and-kettle topography. The knobs are scattered ridges and mounds of debris while the kettles are crevices and pits in the ground, often with collections of water.
  
  A kame moraine is a type of end moraine that exhibits hummocky characteristics, often with knots of sand and gravel that formed via rivers of meltwater.
Rogen or Ribbed Moraine
- Rogen or ribbed moraines have a series of steep ridges of till that developed perpendicular to the direction of the glacier's flow. They are slightly wavy in contour and reminiscent of an animal's ribs.
Supraglacial Moraine
- Forming on the glacier itself, this type of moraine describes any debris that has accumulated on the surface or edges of a glacier, including lateral and medial moraines.
Englacial Moraine
- This type describes any debris that is trapped within the ice, either by falling through cracks or being incorporated as the glacier moves.

Rocks & Minerals