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Chapter 2 Notes
I. The Structure of the Earth
A. Three main layers of the earth
1.
2.
3.
Core – center of the earth made up of iron and nickel
Mantle – surrounds the core and has several layers
 Contains magma, which is molten rock
Crust – thin layer of rock at the earth’s surface
B. Four basic spheres found on and above the earth
1. Biosphere – where plants and animals live
 Consists of the atmosphere, lithosphere, hydrosphere
2. Atmosphere – layer of gases surrounding the earth
3. Lithosphere – solid rock portion of the earth’s surface
4. Hydrosphere – water elements on the earth
C.
Continental Drift Hypothesis
 States that the earth was once a supercontinent that divided and slowly drifted
apart over millions of years.
II. Bodies of Water
A.
B.
C.
Oceans and Seas
 Ocean covers 71% of our planet
 Ocean water circulates by currents, waves, and tides
 Water and air currents carry heat to other places.
Hydrologic Cycle – Evaporation, Condensation, Precipitation, Collection
Ground Water
 Water held in the pores of rock
 Water Table – level at which the rock is saturated
III. Landforms
A.
B.
Landforms – naturally formed features on the surface of the earth
Oceanic Landforms
 Continental shelf – the earth’s surface from the edge of a continent to the deep
part of the ocean.
C.
Continental Landforms


Relief – difference in elevation of a landform from its lowest point to its highest
point.
o 4 Categories of Relief:
1. Mountains
3. Plains
2. Hills
4. Plateaus
Topography – combination of the surface shape and composition of the
landforms and their distribution in a region.
INTERNAL FORCES SHAPING THE EARTH
IV. Plate Tectonics
A.
B.
C.
D.
Tectonic Plates – enormous moving pieces of the earth’s Lithosphere
Plate Movement ( illustrated on pgs. 38 & 39)
1. spreading or moving apart
2. subduction, or diving under another plate
3. collision, or crashing into one another
4. sliding past each other in a shearing motion
Three types of boundaries mark plate movements
1. Divergent boundary – plates move apart, spreading horizontally.
2. Convergent Boundary – plates collide
3. Transform Boundary – plates slide past one another
Folds and Faults
 Folds – rock bends
 Faults – rock cracks
V. Earthquakes
A.
Earthquakes – violent movement of the earth
 Caused by the grinding and slipping of plates along a fault
 Effects of earthquakes:
o Landslides, displacement of land, fires, collapsed buildings, and
tsunamis
 Seismograph – a device that measures the size of the waves created by an
earthquake
 Richter Scale – scale that determines the relative strength of an earthquake
VI. Volcanoes
A. Volcanic Action
 Eruption – hot lava, gases, ash, dust, and rocks explode out of vents in the
earth’s crust, often creating a hill or mountain.
B. Ring of Fire
 A zone around the rim of the Pacific Ocean where 8 major tectonic plates meet.
EXTERNAL FORCES SHAPING THE EARTH
VII. Weathering
A. Two Types of Weathering:
1. Mechanical Weathering – processes that break rock into smaller pieces.
* Does not change the composition of the rock
* Only changes its size
2. Chemical Weathering – rock is changed into a new substance
VIII. Erosion
- Occurs when weathered material is moved by the action of wind, water, ice, or gravity.
A. Water Erosion – water flows in a stream or river picking up loose material and
moving it downstream.
 When a river enters the ocean, the sediment is deposited in a fan-like
landform called a delta.
 Waves reduce or increase beaches
 Sediment deposited by wave action may build up sandbars and islands.
B. Wind Erosion – wind transports and deposits sediment in other locations.
 Landforms produced by wind erosion are: sand dunes, sculpted rocks,
and loess deposits.
C.
Glacial Erosion – glaciers move downslope as a result of gravity.
 Glaciers change the land in the following ways:
o Slice out valleys
o Form hills called moraines
o Leave ridges called eskers
o Create depressions called kettles
IV. Building Soil
A. Weathering and erosion are a part of the process of forming soil.
B. Soils Factors:
 Parent material
 Relief
 Organisms
 Climate
 Time
C. Variety of soils, and the climate in which they are found, determine the types of
vegetation that can grow in a location.