10.4 Water’s Effect on Shaping Earth’s Surface ● Snow has helped shape the rock surface of BC ● Large sheets of moving ice can tear, scrape and carry solid rock. ● Water in its liquid and gas form is also constantly changing the landscape around you. ● These changes can happen quickly or over thousands or millions of years.

Weathering, Erosion, Deposition Weathering is the process of breaking down rock into smaller fragments. Physical weathering: rocks are broken down by physical means. Chemical weathering: a chemical reaction causes rocks to break down Biological weathering: caused by plants or animals After the rock becomes weakened and broken down, it can be carried away in the process of erosion. Deposition is when the material is eventually dropped somewhere, and creates sand dunes and deltas. Sediments deposited in layers may eventually turn into solid sedimentary rock.

Weathering by Water and Ice Physical Weathering is greatest in climates with a lot of moisture in the air or rain and snow, and where there are large temperature differences between winter and summer. Water in the cracks and pores freezes and expands, breaking the rock into pieces. Ice or frost wedging

Chemical Weathering Chemical Weathering is greatest in climates with high temperatures, a lot of rain, and high levels of pollution. Water and oxygen can trigger chemical reactions that decompose minerals and rock Plants die and decompose, releasing chemicals that can break down rocks. When rainwater mixes with carbon dioxide, the water droplets become acidic. When this water reaches the ground, the acid dissolves carbonate rock. The gaps in the rock can create underground caves, sinkholes and an area of sinkholes called karst.

Erosion by Water and Ice Moving water can physically break down rock material into sediment. Sediment is transported and deposited in large amounts elsewhere. Rivers in mountainous or steep regions can carve deep valleys. Rapids can form in a steep and rocky river channel Ocean waves are also a powerful force, eroding coastlines.

Erosion by Water and Ice, con’td Landslides occur when rain soaks the slopes of steep hills and mountains. Glaciers have shaped much of our province’s landscape. Striations are scratch marks left by the glaciers. See p. 394 for the other features created by glaciers.

Deposition by Water and Ice Moving water and glaciers deposit the materials they pick up. A delta is an area of built up sediment deposited where a river empties into an ocean or lake. Glaciers deposit rock material when they melt.