Chapter 1: Intro to Physical Geology
Historical VS. Physical Geology Geology - science of the Earth. Physical - processes and the materials. Historical - order of events, both physical and
biological, that have occurred in the past. The past is the biggest clue to the present.
We do more physical geology is
this class
Physical Geology Topics Plate tectonics. Volcanism. Earthquakes. Landslides. Floods. Mountain-building. Shore erosion. Landscape formation.
Rocks. Minerals. Air. Seawater. Soil. Sand Stream-flow Glaciations
Geologists Use Other Sciences: Chemistry – minerals, rocks, water
Physics - plate tectonics, volcanism, earthquakes.
Biology -how life has changed; fossils
Meteorology – streams, groundwater Oceanography – seafloor spreading, shorelines
James Hutton - (1726-1797)
Father of modern scientific geology Proposed uniformitarianism, -
everything moves slowly in repetitive, continuous cycles. Same processes today have been
operating throughout history. Cycle of uplift, erosion, transport,
deposition, solidification into rock, and renewed uplift takes ……………a LONG TIME.
Earth is 4.55 billion years old.
The Earth’s Interior Earth has 3 main parts:
Core – center, densest part, made of iron & nickel. Mantle - surrounding the core. Crust - surrounding the mantle, thinnest and
outermost
But… of course, it just can’t
be that simple…. There are
sections to sections and more
names to learn…smiles
The Core – more detailed Inner core
High temp + High pressure = solid iron Outer core
Liquid iron
The Mantle – more detailed Lithosphere:
outer 100 km, some crust rocks cooler, more brittle &
rigid
Asthenosphere: 100 to 350 km hot, weak, plastic rocks ductile, little strength, and
easily deformed
Mesosphere between asthenosphere &
outer core core-mantle boundary =
50000C.
How do we know about the core & mantle?
Measure earthquake waves through Earth Waves travel different speeds in solids vs. liquids Compare P & S types of waves Can P waves go through solids? Liquids?
The Crust – more detailed
The crust is not uniform. oceanic crust = about 8 km thick, more dense continental crust = about 45 km thick, less dense
Important Cycles
Hydrologic cycle: Water changing forms and
locations in hydrosphere.
Rock cycle: Rock formed, changed,
decomposed, and reformed by internal and external forces.
Tectonic cycle: Movements of plates of
lithosphere internal processes of Earth’s deep interior that drive plate motions.
The Rock Cycle Rock - natural, nonliving, solid mixture
of minerals Rock cycle describes all the processes by
which rock is: Formed. Transported. Decomposed. Reformed.
3 rock families: Igneous rock - cooling and solidification of
magma Sedimentary rock - formed from deposits of
sediment Metamorphic rock - formed by pressure &
heat on existing rocks
Plate Tectonics Tectonics – study of the movement and deformation of
lithosphere. Plate tectonics theory – lithosphere is cracked in about a
dozen large pieces that constantly move
The Tectonic Cycle Earth releases heat (from core) Hotter magma rises; cooler sinks - convection Helps maintain constant internal temp Convection currents circulate in mantle
moving plates Magma rises & forms new oceanic crust at
mid-ocean ridges. Plates collide and either sink at trenches or build
mountains Lifetime of oceanic crust is shorter than continental
crust.
Results of Plate Tectonics Plate movements and interactions generate:
Earthquakes. Volcanism. Mountain-building. etc.
What’s it called…
in Geology, when everything moves slowly in repetitive, continuous cycles?
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