1. Physical Geography
A Living Planet
The geography and structure of the earth are
continually being changed by internal forces, like
plate tectonics, and external forces, like the
weather.
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2. SECTION 1 The Earth Inside and Out
SECTION 2 Bodies of Water and Landforms
Physical Geography
Looking at the Earth
SECTION 3
SECTION 4
Internal Forces Shaping the Earth
External Forces Shaping the Earth
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3. Section 1
The Earth Inside and
Out
• The earth is the only habitable planet in the
sun’s solar system.
• The drifting of the continents shaped the
world we live in today.
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4. Earth
Continental Puzzle
• The seven continents on earth fit together like a
jigsaw puzzle
• Continents—landmasses above water on Earth
• Francis Bacon (1620) first to suggest 7 continents
were once one
The Earth Inside and Out
SECTION
1
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5. SECTION
1
The Earth’s Neighborhood
• Earth is third planet in the solar system of the sun
• Sun is medium-sized star at edge of the Milky Way
galaxy
• The solar system includes:
- sun and nine known planets
- comets—icy spheres orbiting the sun
- asteroids—large chunks of rocky material
orbiting the sun
The Solar System
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6. The Structure of the Earth
Matters of Size
• Circumference of the earth: about 24,900 miles
• Diameter of the earth: about 7,900 miles
SECTION
1
Inside the Earth
• The core is the center of the earth; made up of iron,
nickel
• Outer core is liquid; inner core is solid
• The mantle surrounds the core:
- has several layers
- contains most of Earth’s mass
Continued . . .
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7. SECTION
1
Inside the Earth
• Magma—molten rock that forms in the mantle
• Crust—thin layer of rock at Earth’s surface
continued The Structure of the Earth
On and Above the Earth
• Atmosphere is the layer of gasses surrounding the
earth:
- contains oxygen
- protects Earth from radiation, space debris
- is the medium for weather and climate
Continued . . .
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8. SECTION
1
On and Above the Earth
• Lithosphere—solid rock portion of Earth’s surface,
forms ocean floor
• Hydrosphere—water elements on Earth including
atmospheric water
• Biosphere—atmosphere, lithosphere, hydrosphere
combined
• Plants and animals live within biosphere
continued The Structure of the Earth
Continued . . .
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9. SECTION
1
continued The Structure of the Earth
Continental Drift
• Continental Drift—1912 hypothesis of Alfred
Wegener:
• Earth once one supercontinent; Wegener calls it
Pangaea, “all earth”
• Pangaea splits into many plates that slowly drift
apart
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10. Section 2
Bodies of Water and
Landforms
• Water covers about three-fourths of the
earth’s surface.
• The earth’s surface displays a variety of
landforms.
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11. Bodies of Water
Ocean Motion
• The ocean circulates through currents, waves, tides
• Currents act like rivers flowing through the ocean
• Waves are swells or ridges produced by winds
• Tides are the regular rising and falling of the ocean
- created by gravitational pull of the moon or sun
• Motion of ocean helps distribute heat on the planet
- winds are heated and cooled by ocean water
Bodies of Water and Landforms
SECTION
2
Continued . . .
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12. SECTION
2
Hydrologic Cycle
• Hydrologic Cycle—cycle of water between
atmosphere, oceans, earth
Lakes, Rivers, and Streams
• Lakes hold more than 95% of the earth’s fresh
water
• Freshwater lakes, like the Great Lakes, are result
of glacial action
• Saltwater lakes form when outlet to sea is cut off:
- streams and rivers carry salts into lake
- salts build up with nowhere to go
Continued . . .
continued Bodies of Water
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13. SECTION
2
Lakes, Rivers, and Streams
• Rivers and streams carry water to and from larger
bodies of water
• Tributaries are smaller rivers, streams that feed into
larger ones
• Drainage basin—area drained by river and its
tributaries
Ground Water
• Ground water—water held in the pores of rock
• Water table—level at which the rock is saturated
continued Bodies of Water
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14. Landforms
Landforms
• Landforms are naturally formed features on Earth’s
surface
SECTION
2
Oceanic Landforms
• Continental shelf—sea floor from continent’s edge
to deep ocean
• Sea floor has ridges, valleys, canyons, plains,
mountain ranges
• Islands are formed by volcanoes, sand, or coral
deposits
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15. Section 3
Internal Forces
Shaping the Earth
• Internal forces reshape the earth’s surface.
• Internal forces shaping the earth often
radically alter the lives of people as well.
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16. Landforms
Continental Landforms
• Relief—difference in landform elevation from lowest
to highest point
• Four categories of relief—mountains, hills, plains,
plateaus
• Topography—the configurations and distribution of
landforms
• Topographic map shows vertical dimensions,
relationship of landforms
Internal Forces Shaping the Earth
SECTION
3
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17. SECTION
3
The Earth Moves
• Tectonic plates are massive, moving pieces of
Earth’s lithosphere
• Plates ride above circulating, heated rock
• Geographers study plate movements to
understand:
- how the earth is reshaped
- how earthquakes and volcanoes are formed
Plate Tectonics
Plate Movement
• Plates move in one of four ways:
- by spreading, or moving apart
- subduction, or diving under another plate
- collision, or crashing together
- sliding past each other in a shearing motion
Continued . . .
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18. SECTION
3
Plate Movement
• Movement of plates effects surface of the earth
• Saudi Arabia–Egypt’s plates are spreading apart,
widening Red Sea
• India’s plate is crashing into Asian continent,
building up Himalayas
• Three types of boundaries mark plate movement:
- divergent boundary
- convergent boundary
- transform boundary
continued Plate Tectonics
Continued . . .
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19. SECTION
3
Folds and Faults
• Two plates meeting can cause folding, cracking of
rock
• Fault occurs when pressure causes rock to
fracture, or crack
• Fault line is place where plates move past each
other
continued Plate Tectonics
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20. SECTION
3
The Earth Trembles
• An earthquake occurs when plates grind or slip at
a fault line
• A seismograph detects earthquakes and
measures the waves they create
Earthquakes
Earthquake Locations
• Location in the earth where an earthquake begins is
called the focus
• Epicenter—the point directly above focus on the
earth’s surface
• Nearly 95% of earthquakes occur at tectonic plate
boundaries
Continued . . .
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21. SECTION
3
Earthquake Damage
• Earthquakes release energy in the form of motion,
causing:
- landslides
- land displacement
- fires (broken gas lines)
- collapsed buildings
• Richter Scale—numeric scale showing relative
strength of earthquake
continued Earthquakes
Tsunami
• Tsunami, a giant ocean wave, begins at epicenter
of an earthquake:
- travels at up to 450 mph
- waves of 50–100 ft. or higher
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22. SECTION
3
The Explosive Earth
• Volcano—underground materials pour from crack
in the earth’s surface
• Most volcanoes occur at tectonic plate boundaries
Volcanoes
Volcanic Action
• Eruption—lava, gases, ash, dust, explode from vent
in Earth’s crust
• Lava—magma that has reached the earth’s
surface; may create landform
Continued . . .
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23. SECTION
3
Ring of Fire
• Ring of Fire—zone around rim of Pacific Ocean:
- meeting point of eight tectonic plates
- vast majority of the earth’s active volcanoes
located here
• “Hot spots” are where magma rises to surface
from mantle
• Hot springs, geysers indicate high temperatures
in earth’s crust
• Some volcanic action is useful:
- volcanic ash produces fertile soil
- hot springs are tapped for heat, energy
continued Volcanoes
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24. Section 4
External Forces
Shaping the Earth
• Wind, heat, cold, glaciers, rivers, and floods
alter the surface of the earth.
• The results of weathering and erosion
change the way humans interact with the
environment.
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25. Weathering
External Forces Shaping the Earth
SECTION
4
Altering the Landscape
• Weathering—processes that alter rock on or near
the earth’s surface
• Can change landscapes over time and create soil
for plant life
• Sediment—mud, sand, silt created by weathering
processes
Mechnical Weathering
• Mechanical weathering—processes that break
rock into smaller pieces
• Does not change rock’s composition, only size
• Examples: frost, plant roots, road construction,
mining
Continued . . .
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26. SECTION
4
Chemical Weathering
• Chemical weathering—interaction of elements
creates new substance
• Example: when iron rusts it reacts to oxygen in air
and crumbles
• Warm, moist climates produce more chemical
weathering than cool, dry
continued Weathering
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27. SECTION
4
Weathered Material Moves
• Erosion—when weathered material moves by
winds, water, ice, gravity
- movement grinds rock into smaller pieces,
carries to new location
• Example: water carries topsoil from hill to river, river
narrows
Erosion
Water Erosion
• Most streams erode vertically and horizontally
- a valley cut by a stream gets deeper, wider;
forms v-shaped valley
- a river deposits sediment at ocean, creates
delta—fan-like landform
Continued . . .
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28. SECTION
4
Wind Erosion
• Wind transports sediment from one place to another
• Loess—wind-blown silt and clay sediment;
produces fertile soil
continued Erosion
Glacial Erosion
• Glacier—large, long-lasting mass of ice; forms in
mountainous areas
• Glaciation—changing of landforms by slowly
moving glaciers
• Example: cutting u-shaped valleys in land
• Moraine—hill or ridge formed by rocks deposited
by glacier
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29. SECTION
4
Soil Formation
• Soil—loose mix of weathered rock, organic matter,
air, water
• Soil supports plant growth; fertility is dependent on
three factors:
- texture
- amount of humus, which is organic material
in soil
- amount of air and water
Building Soil
Continued . . .
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30. SECTION
4
Soil Factors
• When geographers study soil, they look at five
factors:
- parent material—the chemical composition of
the original rock
- relief—the steeper the slope, the greater
erosion; less soil made
- organisms—plants, worms, ants, bacteria
loosen soil; supply nutrients
- climate—hot, cold, wet, dry climates produce
different soils
- time—about 2.5 cubic cm. of soil produced
each century
continued Building Soil
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