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?