GEOL 1001 Chapter : Geology 1001
Geology 1001 Exam One 6/4/2012 11:12:00 AM
-What is Geology?
Geo means earth
What processes formed the mountain belts of western north America?
Why is there abundant oil and gas in Louisiana and the Gulf of Mexico?
Geologists are important and far as Hazard Assessment are concerned.
(volcanoes, earthquakes)
Geologists look at fossil record to see how and when life evolved.
-Geologic Record
James Hutton’s principle of uniformitariasm
“the past is key to the present”
-processes seen today are the same as those of the past
-geologic change is slow; large change requires large amounts of time
The rocks at the bottom of the grand canyon are 1.7-2.0 billion years
old.
The rocks at the top of the grand canyon are about 250 million years
old.
The explosive impact of a meteorite created this 1.2 km wide crater in
just a few seconds.
The Earth System
-Big Bang
The big bang: all mass and energy in a single point
It exploded about 13.7 Ga(billions) of years ago and has been expanding
ever since.
During 1st instant of big bang there was only energy-no matter-present.
Started as a rapid cascade of events
• Protons and neutrons formed within 1 second
• Hydrogen atoms (by 3+minutes) fused to form new light
elements (He, Be, Li, B)
• The universe expanded, cooled and decreased in density.
Heavier elements form during supernovae.
Solar System Formation
• The Nebular Theory
• A nebula forms about 4.56 Ga
o Hydrogen and helium left over from the big bang
o Heavier elements produced by supernovae
• This material collapses into a rotating disc.
• The ball at the center grows dense and hot.
• Fusion reaction begins; the Sun is born.
• Dust in the rings condenses into particles.
• Particles coalesce to from planetesimals.
• Planetesimals accumulates into a larger mass.
• An irregularly-shaped proto-Earth develops.
o The interior heats up and becomes soft.
o Gravity shapes the earth into a sphere.
Shortly thereafter, a Mars sized object hit Earth…and blasted out the
Moon.
During differentiation, Fe (iron and nickel) sank to the center and
lighter elements floated to the surface.
A layered Earth
• Earthquakes-seismic waves that pass through center of Earth
o Wave velocity changes with density.
Earth’s Interior Layers
• Crust
o Continental crust
o Oceanic crust
o The outermost “skin” of Eath with variable thickness.
▪ Thickest under mountain ranges (70 km-40 miles)
▪ Thinnest under mid-ocean ridges (3km-2 miles)
o The Mohorovicic discontinuity is the base of the crust.
▪ The Moho separated the crust from the upper
mantle.
o Continental Crust
▪ Average rock density about 2.8 g/cm3
▪ Average thickness 35-40 km
o Oceanic Crust
▪ Density about 3.0 g/cm3
▪ Average thickness 7-10 km
• Mantle
o Upper
▪ Transition zone
o Lower
• Solid Rock
• 82% Earth’s volume
• below-100-150 km., the rock is hot enough to flow
• transition zone corresponds to an increase in mantle density
w/o a change in composition.
Core
• Outer-liquid
• Inner-solid
Two components with differing seismic wave behavior.
Outer core
• Liquid iron-nickel-sulfur
• T about 3500C.
• Density 10-12 g/cm3
Inner Core
• Solid iron-nickel alloy
• T about 5000C.
• Density 13g/cm3
The Core
• Rapid motion of the liquid outer core stirs up electrical flow in
the solid (Fe) inner core-causing Earth’s magnetic field.
Elemental Composition
• 90% of Earth is comprised of 4 elements
