Download Mantle

GEOLOGY and the Rock
Cycle
GEOLOGIC PROCESSES
 The
earth is made up of a core, mantle, and
crust and is constantly changing as a result
of processes taking place on and below its
surface.
 The earth’s interior consists of:



Core: innermost zone with solid inner core and
molten outer core that is extremely hot.
Mantle: solid rock, under which is the
asthenosphere that is melted pliable rock.
Crust: Outermost zone which underlies the
continents. (Lithosphere)
Spreading
center
Collision between
two continents
Subduction
zone
Continental
crust
Oceanic
crust
Ocean
trench
Oceanic
crust
Continental
crust
Material cools Cold dense
as it reaches material falls
the outer back through
mantle
mantle
Hot
Mantle
material
convection
rising
cell
through
the
mantle
Two plates move
towards each other.
One is subducted
back into the mantle
on a falling convection
current.
Mantle
Hot outer
core Inner
core
Fig. 15-3, p. 337
INTERNAL GEOLOGIC
PROCESSES
 Huge
volumes of heated and molten rock
moving around the earth’s interior form
massive solid plates that move extremely
slowly across the earth’s surface due to
convection currents.

Tectonic plates: huge rigid plates that are
moved with convection cells or currents by
floating on magma or molten rock.
Volcanoes
Abyssal hills
Oceanic crust
(lithosphere)
Abyssal Oceanic
floor
ridge
Abyssal
floor
Trench
Folded
mountain
belt
Abyssal plain
Craton
Continental
shelf
Continental
slope
Continental
rise
Continental crust (lithosphere)
Mantle (lithosphere)
Fig. 15-2, p. 336
Earth
 orbit:
149,600,000 km (1.00 AU) from Sun
 diameter: 12,756.3 km
 mass: 5.972e24 kg
 Earth’s layers (depths in km)




0- 40 Crust
40- 2890 Mantle
2890-5150 Outer core
5150-6378 Inner core
Earth
 Earth’s






mass (measured in 10^24 kg)
atmosphere = 0.0000051
oceans = 0.0014
crust = 0.026
mantle = 4.043
outer core = 1.835
inner core = 0.09675
Earth’s Interior
 Core
is made up mostly of iron/nickel
 Temperatures in core reach 7500 K
 The crust is primarily quartz.
 Taken as a whole, the Earth's chemical
composition (by mass) is:




34.6% Iron
29.5% Oxygen
15.2% Silicon
12.7% Magnesium
2.4% Nickel
1.9% Sulfur
0.05% Titanium
The Earth’s Major Tectonic Plates
Figure 15-4
Major Plates
 North
American Plate
 South American Plate
 Antarctic Plate
 Eurasian Plate
 African Plate
 Indian-Australian Plate
 Nazca Plate
 Pacific Plate
Plate Movement
 The
extremely slow movements of these
plates cause them to grind into one another
at convergent plate boundaries, move apart
at divergent plate boundaries and slide past
at transform plate boundaries.
Figure 15-4
Fig. 15-4, p. 338
JUAN DE
FUCA PLATE
EURASIAN PLATE
NORTH
AMERICAN
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
ARABIAN
AFRICAN PLATE
PLATE
PACIFIC
PLATE
SOUTH
AMERICAN
NAZCA PLATE
PLATE
SOMALIAN
SUBPLATE
CHINA
SUBPLATE
PHILIPPINE
PLATE
INDIAAUSTRALIAN
PLATE
ANTARCTIC PLATE
Divergent plate
boundaries
Convergent plate
boundaries
Transform
faults
Fig. 15-4a, p. 338
Trench
Volcanic island arc
Craton
Transform
fault
Lithosphere
Asthenosphere
Divergent plate boundaries
Lithosphere
Rising
magma
Asthenosphere
Convergent plate boundaries
Lithosphere
Asthenosphere
Transform faults
Fig. 15-4b, p. 338
Convergent Plate Boundary
 Two
plates pushed together
 Oceanic + Continental = Subduction Zone
 Oceanic + Oceanic = Trench
 Continental + Continental = Mountain Range
Divergent Plate Boundary
 Plates
moves apart from one another
 Oceanic plates form oceanic ridges
Transform Faults
 Plates
slide and grind past one another along
a fracture in the lithosphere
Benefits of volcanoes, earthquakes,
and tsunamis
 Geological:


Recycle rock and earth’s crust
Form minerals
 Ecological:



Speciation (due to isolation)
Maintaining atmosphere thus climate
Enrich soils = more food
Geologic Time Scale
 ~4.6
billion years ago: Earth believed to have
formed, hot ball of rock
 3.9 billion years ago: rainstorms
 3.5 billion years ago: oceans, first living
organisms
Geologic Eras


Precambrian Era: 4.6 billion years ago- 545 million years
ago
 87% of Earth’s history
 Prokaryotes dominated
 First eukaryotes appeared ~ 1.5 billion years ago
 Simple multicellular organisms in seas
Paleozoic Era: 545 million years ago – 248 million years
ago
 “Explosion of life”
 Many types of invertebrates in shallow seas
 Early: earliest vertebrates
 Middle: amphibians
 Later: reptiles
Geologic Eras


Mesozoic Era: 248 million years ago – 65 million years ago
 Triassic: mammals made first appearance
 Jurassic: “age of dinosaurs”
 Cretaceous: radiation of mammals and evolution of
flowering plants
 Plate Tectonics: continental shift
Cenozoic Era: 65 million years ago – now
 Mammals flourish
 Primates evolve
 Extinctions affect diversity
 Modern human species evolved ~200,000 years ago
EXTERNAL GEOLOGIC
PROCESSES
 Surface

processes
Based largely on energy from the sun and gravity
 Tends
to wear down Earth’s surface and
produce a variety of landforms by the buildup
of eroded sediment
 Erosion
 Weathering
Wearing Down and Building Up the
Earth’s Surface
 Weathering
is an
external
process
that wears
the earth’s
surface
down.
Figure 15-6
EROSION
 Process
by which material is dissolved,
loosened or worn away from one part of the
earth’s surface and deposited in other places
 Streams are most important agents of
erosion
MINERALS, ROCKS, AND THE
ROCK CYCLE
 The
earth’s crust consists of solid
inorganic elements and compounds
called minerals that can sometimes be
used as resources.

Mineral resource: is a concentration of
naturally occurring material in or on the
earth’s crust that can be extracted and
processed into useful materials at an
affordable cost.
Nonrenewable mineral resources
 Fossil
fuels (oil, natural gas, coal)
 Metallic minerals (Al, Cu, Fe)
 Nonmetallic minerals (sand, gravel,
limestone)
Minerals and their Uses
Metals
 Al- building, cans
 Steel- building
 Cu- conductor,
electronics
 Mn, Co, Cr- used in alloys
 Pt- catalytic converters
Nonmetals
 Sand- glass, concrete,
bricks
 Gravel- roadbeds
 Limestone- roadbeds,
natural buffer
 Phosphate saltsfertilizers
US consumption
 8%
of world population but use 75% of
metals on earth

Uses: cars, engines, appliances, weapons,
satellites
ROCK

A very slow chemical cycle recycles three types of
rock found in the earth’s crust:



Sedimentary rock (sandstone, limestone). Formed from
sediment of pre-existing rocks that are weathered and
eroded
Metamorphic rock (slate, marble, quartzite). Formed
when pre-existing rock is subjected to high temperatures
or pressure
Igneous rock (granite, pumice, basalt). Formed from
cooled magma at or below earth’s surface
Erosion
Transportation
Weathering
Deposition
Igneous rock
Granite,
pumice,
basalt
Sedimentary
rock
Sandstone,
limestone
Heat, pressure
Cooling
Heat, pressure,
stress
Magma
(molten rock)
Melting
Metamorphic rock
Slate, marble,
gneiss, quartzite
Fig. 15-8, p. 343