What is a moraine?

A moraine is specifically defined as a glacial landform that is formed from the accumulation of till, which is the unsorted debris left behind by glaciers. As glaciers advance, they pick up rocks and sediment from the terrain, and when they retreat, they deposit this material, creating distinct ridges or mounds known as moraines. These formations can vary in size and shape and are essential in understanding the historical movement of glaciers and the geological features of the landscape.

The other choices do not accurately reflect the definition of a moraine. A type of sedimentary rock refers to geological materials formed through various processes of sedimentation, which is unrelated to glacial deposits. Similarly, volcanic eruptions create different geological features, such as lava flows or ash deposits, rather than moraines. Coastal sediment formations are associated with processes like erosion and deposition along shorelines, which also differ from the processes that create moraines associated with glacial activity. Understanding moraines helps in the study of past climates and geological history linked to glacial movement and earth's surface changes.