Earth:
Geology
February
24, 2000
Announcements
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HOMEWORK
#3
on web
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Solutions
to homework #2 on web
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QUIZ
THIS WEEK IN DISCUSSION SECTION
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Covers
chapters 1-6
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22
multiple choice test problems (similar to midterm/final)
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1 longer
answer like homework (worth 3 multiple choice problems)
Basic
Earth Data
Surface
Properties
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3/4 of Earth's surface covered
with water
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average surface temperature
of 70o F
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water is, on average, liquid
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water probably came from
icy planetesimals
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Land and sea beds composed
of rocks
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Igneous -- cooled magma/lava
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Sedimentary -- old lake/sea
bottom
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Metamorphic -- squished
What
are Rocks Anyway?
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Rocks are (combinations of)
minerals
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Minerals are in turn composed
of one or more elements
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single elements:
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Gold -- gold
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Diamond -- carbon
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More than one element
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Quartz -- silicon, oxygen
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Feldspar -- silicon, aluminum,
oxygen
Quartz, Feldspar, Mica
Types
of Rocks
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Igneous rocks
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mineral soup
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magma (under surface)
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lava (above surface)
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Basalt, Granite
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Sedimentary rocks
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mineral sandwiches
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lake and ocean beds
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Limestone, Sandstone (Wisconsin)
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Metamorphic rocks
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squished rock
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rock becomes (re)buried,
high pressures and temperatures metamorphose the rock
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Marble, Schist
Lava
Basalt, Granite
Limestone, Sandstone
Marble, Schist
Journey
to the Center of the Earth
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In hot protoplanet Earth,
heavy stuff like iron (Fe) sank
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Lighter stuff like silicon,
aluminum and oxygen (Feldspar) floated
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Earthquake studies reveal
layered structure of Earth's core
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waves from earthquakes (seismic
waves) travel through the earth!
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like refraction of light
in glass, these waves bend at sharp material boundaries
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allow mapping of inner layers
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we can't go there but seismic
waves can
Types of waves from earthquakes
Onion
Earth
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inner
core, outer core, mantle, crust
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outer
mantle is plastic (flows slowly)
Plate
Tectonics
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Sections of the crust move
relative to each other slowly
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Evidence: similar rocks in
different places
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Sensitive instruments can
measure yearly motion
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Pangaea 200 million years
ago
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Laurasia, Gondwanaland 100
million years ago
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Compare to age of Earth 4-5
billion years -- may have been earlier versions of Pangaea
Earthquakes
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Earthquakes
are caused by plate tectonics
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Plates
often stick when moving relative to each other
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earthquake
happens when plates slip
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Plate
motion caused by convection in the Asthenosphere (soft upper mantle)
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Plates
are part of the lithosphere
Hot
Spot Volcanism
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Volcanos
happen where crust is thin
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Plate
boundaries
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Hot
spots like Hawaii
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Hawaii's
hot spot remains fixed, plate moves
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Venus
and Mars have hot spot volcanism but no plate motion -- BIG volcanos
Geology
Summary
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Earth's surface 75% water
-- different from other terrestrial planets
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Rocks are mineral(s)
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Igneous, Sedimentary, metamorphic
rocks
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Earth: inner core, outer
core, mantle, crust
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Crust divided into plates
-- unique among terrestrial planets
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Plates move because of convection
in upper mantle
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earthquakes
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continental drift, Pangea
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Volcanos -- hot spot volcanism