Download APES-Chapter-16-Geology-PPT-Part

Chapter 16
Geology and Nonrenewable
Mineral Resources
What is the Earth’s Structure?
• Core: Earth’s innermost zone; very hot;
solid inner part surrounded by a liquid core
• Mantle: surrounds the core; mostly solid
rock; outermost part is very hot, partly
melted rock (like flowing plastic)
• Crust: outermost and thinnest zone;
consists of the continental crust (underlies
continents) and the oceanic crust
(underlines oceans)
35 km (21 mi.) avg., 1,200˚C
Crust
100 km (60 mi.)
200 km (120 mi.)
Low-velocity zone
Mantle
Solid
10 to 65km
2,900km
(1,800 mi.)
3,700˚C
Outer core
(liquid)
Core
Inner
core
(solid)
100 km
200 km
5,200 km (3,100 mi.), 4,300˚C
Earth’s Crust and Mantle
Abyssal
floor
Trench
Volcanoes
Abyssal plain
Abyssal Oceanic
floor
ridge
Oceanic crust
(lithosphere)
Mantle (lithosphere)
Mantle (asthenosphere)
Continental
slope
Continental
shelf
Continental crust
(lithosphere)
Mantle
(lithosphere)
Abyssal plain
Movement of Heat within the Earth
•
Internal Processes: originate from the Earth’s
interior
• Decay of radioactive elements in the crust
adds to heat within the mantle
• Two types of heat movement happen inside
the mantle:
1. Convection Cells: large volumes of heated
rock move (like pot of boiling water)
2. Mantle Plumes: mantle rock flows upward in a
column (like smoke from a chimney)
What are Tectonic Plates?
• Convection cells and mantle plumes both
move upward as heated material is
displaced by cooler, sinking material
• These flows of energy cause movement of
“tectonic plates”
• Plates are about 60 miles thick
• Composed of continental and oceanic
crust, and the outermost part of the mantle
Oceanic tectonic
plate
Collision between
two continents
Spreading
Oceanic tectonic
center
plate
Ocean trench
Plate movement Plate movement
Tectonic plate
Oceanic
crust
Continental
crust
Continental
crust
Material cools
as it reaches
the outer
mantle
Cold dense
material falls
back through
mantle
Hot material
rising
through
the mantle
Two plates move
towards each other.
Mantle
Hot outer
Inner
core
core
More about Plate Tectonics
• Tectonic plates move constantly, like large
pieces of ice on lake surface
• Move about the rate of fingernails growing
• Widely accepted theory in the 60s.
• Throughout history, continents have drifted
apart and joined together as plates move
back and forth across Earth’s surface
More about Plate Tectonics
• Produces mountain and ocean ridges
• Volcanoes and earthquakes are found at
plate boundaries
• Allows us to trace how species migrated
from one area to another
Earthquake and Volcano Sites
Volcanoes
Earthquakes
Boundaries Between Earth’s Plates
• Divergent Plate Boundaries: plates move
in opposite directions
• Convergent Plate Boundaries: plates are
pushed together by internal forces; forms
a trench
• Transform Faults: occur where plates slide
past one another; most are on the ocean
floor
Between Earth’s Plates
• External Processes: geological changes
based on energy from the sun or gravity
• Erosion: material is dissolved, loosened,
or worn away from one part of the Earth’s
surface and THEN deposited in other
places
• Wind can cause erosion as soil is blown
from one area to another
• Human activities accelerate erosion
Continued…
•
Weathering: process that loosens
material that can be eroded
• Two Types of Weathering:
1. Mechanical Weathering: large rock mass
is broken into smaller fragments; Frost
Wedging (water collects in pores of
rocks, expands, and splits rock)
2. Chemical Weathering: chemical
reactions decompose a mass of rock
Lake
Tidal
flat
Glacier
Spits
Stream
Dunes
Lagoon
Shallow marine
environment
Barrier
islands
Delta
Dunes
Beach
Shallow marine
environment
Continental shelf
Continental slope
Continental rise
Volcanic
island
Coral reef
Abyssal plain
Minerals and Rocks
• Earth’s crust is composed of minerals and
rocks
• Mineral: element or inorganic compound
that occurs naturally and is solid (gold,
silver, salt, quartz)
• Rock: any material that makes up a large,
natural, continuous part of the Earth’s
crust; most rocks consists of two or more
minerals
Three Major Types of Rocks
1. Igneous Rock: formed below or on Earth’s
surface when magma (molten rock) wells up,
cools, and hardens into rock (granite, lava
rock)
2. Sedimentary Rock: formed from sediment
when rocks are eroded, transported to another
place, and deposited in water (sandstone)
3. Metamorphic Rock: rock is subjected to high
temperature, high pressure, or chemically
active fluids (coal, slate, marble)
Rock Cycle
• Rocks are constantly exposed to changing
conditions
• Interaction of processes that change rocks
from one type to another is called the
Rock Cycle
• Slowest of all Earth’s cycles; recycles
material over millions of years
Transportation
Sedimentary Rock
sandstone,
limestone
Deposition
Erosion
ROCK CYCLE
Weathering
Heat,
pressure,
stress
EXTERNAL PROCESSES
INTERNAL PROCESSES
Igneous Rock
Granite, pumice,
basalt
Heat, pressure
Cooling
Metamorphic Rock
Slate, marble,
Melting
Magma
(molten rock)
Earthquakes
• Stress in the Earth’s crust can cause solid
rock to deform until it fractures and shifts
along the fracture (fault)
• Abrupt movement of an existing fault
causes an earthquake
• When fracture happens, energy is
released as shock waves
Measuring Earthquakes
• Magnitude: severity of an earthquake
• Measure amount of energy released in an
earthquake
• Categories: insignificant, minor, damaging,
destructive, major, great
• Each level is 10x greater than the previous
How Can We Reduce
Earthquake Hazards?
• Examine historical records and make
measurements to locate active fault zones
• Make maps to show high-risk areas
• Establish building codes for high-risk
areas
• Try to predict where and when
earthquakes will occur
Volcanoes
• Occurs where magma (molten rock)
reaches the Earth’s surface through a
crack
• Volcanic activity can release: debris (hot
lava rock or ash), liquid lava, gases
• These gases may become concentrated in
the atmosphere and become concentrated
into sulfuric acid
extinct
volcanoes
Volcano
central
vent
lithosphere
Upwelling
magma
magma
reservoir
Aftermath of Volcanoes
• Between 1985 and 1999: 561,000 people
died from natural disasters; about 30% of
these were from earthquakes and volcanic
eruptions
• Benefits: scenery, lakes (Crater Lake in
Oregon), fertile soil from weathering lava
How Can We Reduce Volcano
Hazards?
• Land-use planning
• Better prediction of volcanic
eruptions
• Evacuation plans