Earth

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Chapter Twenty Two
Earths Interior
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Crust - the outermost thinnest layer of Earth
(oceanic continental) (deepest we can go)
Mantle - the layer of rock between the Earth's
crust and its core (80 of Earths volume)
- outer mantle made up of solid rock
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- inner mantle has extremely hot rock that is
soft and easily deformed
Lithosphere - the thin outer shell of Earth,
consisting of the crust and upper mantle (60 mls)
Asthenosphere - the zone of the mantle beneath
the lithosphere that consists of slowly flowing
solid (but soft) rock
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Core - the center of the Earth (outer is liquid
metal, inner is solid metal)
p. 662-663
- the Earths interior gets hotter with depth
- heat comes from radioactive isotopes in the
interior
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Minerals and Rocks
Mineral - a natural, inorganic solid with a
definite chemical composition and a charact-
eristic internal structure
- 4000 known minerals in the Earths crust (only
twenty commonly found in rocks that make up 95
of all rocks)
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Igneous rock - rock formed from cooled and
hardened magma or lava
Extrusive igneous rock - cooled ABOVE the
Earths surface
Intrusive igneous rock - forms from magma that
cools while trapped BELOW the Earths surface
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Weathering - the process by which rocks are
broken down and as they accumulate they form
another type of rock
Sedimentary - rock formed from compressed or
cemented deposits of sediment (recycled rock)
including fossils
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Fossils - the traces or remains of a plant or
an animal found in sedimentary rock
From sediment to rock
- sediment is just compressed from the weight of
sediment above
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- other minerals dissolved in water seep between
bits of rock and glue them together
Sedimentary rocks are named according to the
size of the fragments they contain
Conglomerate - a rock made of pebbles
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Sandstone - a rock made of sand
Shale - fine mudstone that breaks easily into
layers
Limestone - made mostly of the fossils of
organisms that lived in water
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Metamorphic Rock - formed from other rocks as the
result of heat, pressure, or chemical processes
without ever melting
Limestone becomes marble
Shale becomes slate
Know the Rock Cycle on p. 675!!!
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Plate Tectonics - the theory that the earths
surface is made up of large moving plates
- move 0.4 to 6.3 inches per year
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Plate Tectonics
- Alfred Wegener was the first to notice fossils
of the same kinds of animals on different
continents
- he said they must have been connected (Pangaea)
- not until the 1960s did continental drift
become a valid explanation
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Why They Move
Asthenosphere - the zone of the mantle beneath
the lithosphere that consists of slowly flowing
solid (but soft) rock
- some scientists believe the plates move due to
convection currents located here
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Divergent Plate Boundaries
- when two plates move apart, creating a gap
between them
- magma then rises to the surface and forms new
lithospheric rock
Mid-Ocean Ridges - mountain ranges that form at
divergent boundaries
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Rift Valley - large central valley surrounded by
high mountains
(Mid-Atlantic Ridge is most studied)
Convergent Plate Boundaries
- oceanic plates dive beneath other plates
destroying lithosphere (ocean plates are more
dense)
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Subduction - the process in which a tectonic
plate dives beneath another tectonic plate (Zones)
Mariana Trench - in the P.O., is the deepest
(6.8 miles)
Continental plates collide to form mountains
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Transform Fault Boundaries
- plate movement can cause cracks in the
lithosphere in other places
- this creates faults which are a crack in the
earth created when rocks on either side of a
break move
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Evidence for Plate Tectonics
- (p. 679)
- as hot rock pours onto the ocean floor
the iron type minerals align themselves
parallel to the Earths magnetic field then
harden with that alignment
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- the rock record shows alternating bands of
rocks that show the earth magnetic field has
changed
- young rock is nearest the ridge, old rock is
farther away
Earthquakes and Volcanoes
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- earthquakes are the result of the lithosphere
vibrating due to movement along a plate boundary
or a fault (vibrations are called Seismic Waves)
- p. 686
Focus - area along a fault at which slippage
first occurs, initiating an earthquake
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Epicenter - the point on the Earths surface
directly above the focus of an earthquake
Earthquake Waves
- transfer the energy
P Waves - primary waves, originate from the
focus (are longitudinal)
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S Waves - secondary waves, also originate from
the focus (are transverse)
Surface Waves - moves across the earths
surface and they bend reshape the surface
- roll like ocean waves and cause much
destruction
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Seismology - study of earth- quakes and related
phenomena
Richter Scale - scale that expresses the
relative magnitude of an earthquake
- each step represents a 32x increase in energy
- does not predict damage
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Earthquake Damage - Factors
- distance from epicenter to populated areas
- depth of focus (deeper less)
- properties of rocks (hard less)
- building construction
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Volcanoes - an opening in the Earths crust thru
which magma has reached the surface
Magma - molten rock below the surface of the
Earth
Lava - molten rock above the surface of the
Earth
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Shield Volcano - gently sloping mountain with
mild eruptions built up by slowly flowing lava
Composite Volcano - steeper mountain with
alternating layers of ash, cinders, and lava
(eruptions can be flows and/or violent ones)
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Cinder cones - the smallest most abundant
volcanoes (mostly violent eruptions)
- often lie dormant for years
Seamounts - volcanoes that form under the oceans
(look like composite Vs)
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Volcanoes occur at convergent boundaries (Ring
of Fire), divergent boundaries (Iceland),
and in the middle of plates (Hot Spots like the
Hawaiian Islands)