The Earth’s Changing Surface

What is Weathering? Weathering is the chemical and physical processes that break down rock at Earth’s surface. There are two types of weathering: Chemical & Physical

Mechanical (Physical) Weathering The type of weathering in which rock is PHYSICALLY broken down into smaller pieces. Abrasion, Freeze/Thaw, Plant growth

Ice Wedging Repeated freezing and thawing of water in cracks of a rock. Water seeps into cracks in rock and then freezes. Rock is pushed apart by frozen water.

Plant Growth Roots act as wedging, causes cracks in the rock. Roots exert constant pressure on rock. Eventually breaking them apart.

Acid Rain, Oxygen/Rust, Living Organisms, acid digest rock Chemical Weathering The process that breaks down rock through chemical changes. Acid Rain, Oxygen/Rust, Living Organisms, acid digest rock

Carbon Dioxide Carbon Dioxide from the air dissolves in rainwater. Result: water that contains carbonic acid. A weak acid that reacts with minerals to break down the rock. Limestone caves

Water Hydrolysis: the change in composition of minerals when they react chemically with water. Leaching: process of transferring dissolved minerals to lower layers of rock

Acid Rain Rain contains carbonic acid. Fossil fuels release sulfur dioxide and nitrogen oxides that react with water to form sulfuric acid and nitric acid. falls to Earth as acid rain

What is Erosion? Erosion –the process by which natural forces move weathered rock and soil from one place to another. It wears away parts of the Earth’s surface. Gravity, running water, wind, waves, ice, underground water

Erosion (cont.) Sediment – is the material moved by erosion. Sediment may consist of: pieces of rock soil remains of plants and animals Both weathering and erosion produce sediment.

What is Deposition? Deposition – drops weathered material (sediment) in new places. The process by which material is laid down. It changes the shape of the land by building new land forms.

Weathering, erosion, and deposition act together in a cycle that wears down and builds up the Earth’s surface. Erosion and deposition are at work everywhere on Earth The cycle of erosion and deposition is never-ending.

Mass Movement Gravity is the force that moves rock and other materials down hill. Gravity causes mass movement The different types of mass movement include landslides, mudflows, slump, and creep. Mass movement can be fast or slow.

Landslides This is the most destructive type of mass movement. Landslides occur when rock and soil slide quickly down a steep slope. Some landslides contain huge amounts of rock and soil, some only contain small amounts of rock and soil.

Mudflows A mudflow is the rapid downhill movement of a mixture of water, rock, and soil. Mudflows often occur after heavy rains in a normally dry area. Under certain conditions, clay soils suddenly turn to liquid and begins to flow. An earthquake can trigger both mudflows and landslides.

Slump A mass of rock and soil suddenly slips down a slope. The material in a slump moves down in one large mass.

Creep Creep is the very slow movement of rock and soil. Creep is so slow you can barely notice it. Bent trees Cracked roads Leaning poles/fences