GLG 111 Lecture Notes - Lecture 1: Inner Core, Continental Crust, Asthenosphere
ORIGINS OF UNIVERSE, SOLAR SYSTEM, AND
EARTH’S STRUCTURE 18:42
Science based on assumption that the natural world behaves in a predictable
manner that can be understood thru careful systematic study. The scientific
method therefore is used by scientists to test their hypotheses and validate
their observations about the natural world
Observation and question -> form a hypothesis -> test hypothesis -> accept
modify of reject hypothesis
Examples
Observation – outcrop of mudstone shale and limestone in Ohio
Hypothesis – these rocks were deposited in an aqueous environment
Test – look for evidence of aquatic plant and animal fossil
If all evidence supports the hypothesis then accept. If not modify or reject
the original hypothesis and try again
Geology – science that pursues an understanding of earth, its history and
its components and its physical and chemical characteristics
Two broad areas of geology
Physical geology – this course focuses on this
Historical geography
Origins of geology
Earth has been the focus of study for centuries
Greeks (Aristotle) wrote about natural phenomena: fossils, volcanoes,
earthquakes etc.
These early thoughts were not based on observations or experiments
James Hutton – father of modern geology – developed uniformitarianism
Uniformitarianism – the present is a key to the past – states that that
physical, chemical and biological laws also operate today also operated in
the geologic past
Origins of the universe
Big bang theory
find more resources at oneclass.com
find more resources at oneclass.com
Incomprehensible explosion that sent all matter of the universe flying
outward
The first elements to form were hydrogen and helium
Over billions of years this debris began to cool and condense into bodies
(like galaxies, stars, planets)
Nuclear fission is where the energy comes from
Origin of earth: nebular hypothesis
Proposes that all the bodies in our solar system evolved from an enormous
rotating cloud of elements gas and dust about 4.5 billion yrs. ago
Evidence comes from meteorites – meteorites are about 4.55 bill. Yrs. old –
so all material in our solar system was formed around that time – represents
early stages of our solar system
Nebula is location where stars are born – extremely dense cloud of gas dust
and elements
Nebular hypothesis:
A) Solar nebula contracts – under influence of gravity
B) Nebula forms rotating disk – gravity is pulling this together
C) Continued gravitational collapse causes the nebula to form a rotating disk
– becoming more dense in center
D) Increased heat and pressure forms a proto-sun and plantelestimals (early
planets)
E) Fusion begins – forming our sun – this form the solar winds that push the
light elements to the outer reaches of our solar system – dense elements
remain near sun
F) Our solar system – the solar system is organized w the rocky planets
closest to sun and the gaseous planets farther away from the sun
99% of solar system mass is sun
As u move outwards from sun becomes less dense
Earths internal structure
Earths interior characterized by a gradual increase in T and P
This changes the chemical and physical properties of the rocks
Rocks may melt
Rocks become more dense
Dense materials sink and less dense materials floats
As we descend into earth the temp. And pressure goes up
find more resources at oneclass.com
find more resources at oneclass.com
How do geologists know what the interior of the earth looks like?
Earthquakes, rocks from earths interior, meteorites
Earthquakes
Earthquakes release seismic energy (waves)
P waves – can pass thru solids and liquids
S waves – can pass thru only solids
P waves can pass thru all of earth but s waves stops at outer core so we
know outer core is a liquid b/c s waves cant go thru liquid
Sound waves move faster thru dense rocks
S and p waves become faster with depth
P waves decrease rapidly at outer core – so we know it’s a liquid
Rocks
Volcanic eruptions bring molten rock to the earths surface
These eruptions also bring rock fragments from within the earth – get an
idea of chemicals w/in the earth
Mantle xenoliths
Kimberlitic eruptions (diamonds)
Meteorites
Meteorites are believe to be debris formed by the collisions during our solar
systems early history
Earths internal structure
Interior can b divided into chemical and physical divisions
Chemical divisions – based on compositional differences
Physical divisions – based on the physical behavior of the rocks
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Science based on assumption that the natural world behaves in a predictable manner that can be understood thru careful systematic study. The scientific method therefore is used by scientists to test their hypotheses and validate their observations about the natural world. Observation and question -> form a hypothesis -> test hypothesis -> accept modify of reject hypothesis. Observation outcrop of mudstone shale and limestone in ohio. Hypothesis these rocks were deposited in an aqueous environment. Test look for evidence of aquatic plant and animal fossil. If all evidence supports the hypothesis then accept. If not modify or reject the original hypothesis and try again. Geology science that pursues an understanding of earth, its history and its components and its physical and chemical characteristics. Physical geology this course focuses on this. Earth has been the focus of study for centuries. Greeks (aristotle) wrote about natural phenomena: fossils, volcanoes, earthquakes etc. These early thoughts were not based on observations or experiments.
