Post on 24-Feb-2016
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EARTH AND ITS
RESOURCESForces that Shape the Earth
Chapter 5, lesson 4
WHAT IS WEATHERING? Weathering: the breaking down of rock
into smaller pieces by natural process IceMoving WaterVegetation
TWO TYPES OF WEATHERING
1. PHYSICAL Breaking down of rock
by physical movements Water Plants Animals
Frost wedges into cracks and expands
Moving water carries pieces of rock
Plants root under rocks and grow
Animals burrow and bring pieces underground
TWO TYPES OF WEATHERING(CONT.)2. CHEMICAL
Breaking down of rock by changes in its chemical composition Oxygen VS iron Acids
Rocks contain iron which reacts with oxygen in the air
Oxygen and iron make rust, which makes the rock less strong than it was before
Carbonic acid, or acid rain, can wear away at natural limestone
EROSION AND DEPOSITION
Erosion is the picking up and removing of rock pieces
Deposition is the dropping off of particles in another location
Wind contributes to erosion Carries small particles in the
wind Shapes sand dunes
Water contributes to erosion Freezing and thawing changes
landscape Melting snow affects soft rocks
EROSION AND DEPOSITION (CONT.)
Flowing water is a major cause of erosion
When the river slows down, some of the particles are deposited as sediment, or loose pieces of rock
This can cause the river to meander, or curve
HOW CAN MOVING WATER CHANGE THE LAND?
Gravity and glaciers are other agents that cause erosion
Glaciers form when more snow falls than it can melt When ice sheets are about 100 meters thick, it
begins to fall downhill When it falls, it takes loose pieces of land with it This mixture of land pulled loose by glaciers is called till These deposits take the form of a ridge or mound, called
a moraine
HOW IS SOIL FORMED? Weathering results in loose rock
pieces which become a part of soil
Soil: a mixture of weathered rock, air, water, living things, and humus Humus: material made of decayed
plant and animal remains Bacteria, fungi, worms, and insects
all contribute to the formation
When plants or animals die, their remains enrich the soil and develop layers called soil horizons
WHY IS SOIL IMPORTANT? Minerals in soil cannot be replaced, it must be
conserved Soil can be ruined by…..
Growing too many plantsOr the same plants many years in a row
Dumping waste in soilPaving over landBuilding dams