Question

How do erosion and deposition work together to create a moraine?

Waves cause erosion along coastlines and deposit sand away from the shore.
Surface water in rivers causes erosion, carrying sediment that gets deposited near an ocean.
Glaciers cause erosion as they melt, carrying sediment that gets deposited in a thick layer.
Winds cause erosion by blowing around sand that gets deposited in large piles.

Answer 1

The correct choice is the third one: "Glaciers cause erosion as they melt, carrying sediment that gets deposited in a thick layer."

How that makes a moraine (briefly):
- Moving glacier ice erodes bedrock and loosens rock fragments by plucking and abrasion, carrying rock debris within and on top of the ice.
- When the glacier slows or melts back, its ability to carry debris falls and the material is dropped. The dumped, unsorted mix of clay, sand, gravel and boulders is called till.
- That till can build up into ridges or mounds called moraines (terminal moraines at the glacier front, lateral moraines along the sides, medial moraines where two glaciers join, and ground moraines beneath the ice).

Notes on the other statements:
- Waves erode coasts and deposit sand to form beaches (not moraines).
- Rivers deposit sediment in deltas or floodplains (sorted by water).
- Wind deposits create dunes (also sorted).
Glacial deposition is distinct because it leaves unsorted till and ridge-like moraines.