Geology

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Geology

• Means terrestrial geology (the Earth)
• Materials
• Rocks
• Minerals
• Atmosphere
• hydrosphere

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Why study the Earth?

• Cheap
• Complex
• Interesting
• Serves as a model for the other planets

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• Processes
• Weathering of rocks
• Transport of debris
• Formation of new rocks
• Life processes

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Interior of the Earth
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Interior of the Earth

• Iron core
• Denser, darker rocks (mantle)
• Lighter, less dark rocks (crust)
• Separated by density
• Iron at bottom
• Crust at top
• Stable configuration

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But

• Earth is hotter at bottom than at top
• So, in the mantle, the hot material at the bottom
  wants to rise (less dense)
• And, the cooler material at the top wants to sink
  (denser)
• This is the heat engine of the Earth

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Mantle

• Largely solid material
• But hot, solid material
• So, the hot stuff at the bottom tends to rise
• And the cooler stuff at the top tends to sink
• This is a convection cell
• And that is what makes the Earth a dynamic place

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Crust

• Relatively thin
• Brittle
• Two kinds
• Continental
• Less dense
• Lighter in color
• Oceanic
• Dense
• Dark colored

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Evidence of heat

• Geysers
• Volcanoes
• Earthquakes
• Temperatures in deep mines
• Heat flow measurements
• Origin of heat
• Radioactive decay

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Kinds of rocks

• Sedimentary rocks
• Originally from small particles
• Sand
• Silt
• Clay
• gravel
• Which were transported
• Wind
• Water
• Ice

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• And then cemented together
• By other minerals
• We get several kinds of sedimentary rocks
• Sandstone
• Limestone
• Shale
• Siltstone
• Need
• Atmosphere and
• water

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Igneous rocks

• Pre-existing material (some sort of rock)
• Heated and
• Melted to form magma
• Then cooled
• Slowly or
• Quickly
• Slow cooling gives large crystals
• Rapid cooling gives small crystals

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• Slow cooling
• Granite
• Rapid cooling
• Lava (typically basalt lava)
• Need
• Heat (comes with depth)
• A means of burying rock

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Metamorphic rocks

• Some sort of rock which is
• Heated and squeezed (typically by burial)
• Slate
• Marble
• Not melted

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Convection cells in liquid
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Convection in the mantle whole or just part.
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Convection cells in the mantle
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Upper part of the Earth is split between the
lithosphere and the asthenosphere. Based on
physical properties.
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Spreading center here the split is in a
continental region
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Spreading center here the split is in the
oceanic crust
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Subduction zone here the melting of the
subducted material is forming a chain of
volcanoes.
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Effects of plate tectonics

• Over time the continents appear to move around
  the surface of the Earth
• Oceans are not permanent features
• Over time the continents have grown in area
• As the continents have moved, the climate has
  changed

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200 million years ago
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Evidence for ancient glaciation
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Evidence for the plate movement in the Pacific
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Types of plate boundary
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To identify plate tectonics

• Linear chains of volcanoes
• Linear trenches
• Water (?)
• Earthquakes (?)
• Heat flow measurements