Download Introducing Geology

Introducing Geology
What is Geology?
• Geology - the scientific study of Earth.
– Physical Geology is the study of:
• Earth Materials
– Minerals
– Rocks
Geology
• Processes that Occur on Earth’s Surface
– Weathering, the natural decomposition of minerals
and rocks. The final product of weathering is soil.
Brice Canyon, UT
Surface Processes
• Erosion - Movement of Weathered Earth
materials on Earth’s surface
Surface Processes (cont.)
• Uplift
– Volcanic and/or tectonic forces build crust up above
sea level
Uplift
– Removal of material by erosion allows
isostatic uplift of underlying continental rocks.
Isostasy
• Archimedes’ Principle
– Every floating object is pushed upward by a buoyant
force that is
• Equal to the weight of the displaced fluid
Figure 1-16A
Isostasy (Greek for “equal standing”)
• Earth’s crust consists of
buoyant blocks of rock.
– They float in gravitational
balance on top of the
mantle
• Isostatic equlibirum
– Occurs when the buoyant
force equals the
opposing gravitational
force.
– Equilibrium Line
• Separates the iceberg’s
submerged root from its
exposed top.
Figure 1-16
Surface Processes (cont.)
• Deposition
– Loose sediment is deposited in low areas when transport agent
(water, ice, wind) loses its carrying power
– Earlier sediments get buried by later ones and harden into
sedimentary rock
Structure and Processes of
Earth’s Interior
Gravity Meter
Magnetometer
Seismographs
Tectonics
• The study of the origin and arrangement of
Earth’s structural features which include
– Folds and faults but also
– Continents
– Mountains
– Earthquake regions.
Plate Tectonics
• Earth’s lithosphere (the crust and the rigid
upper mantle) is divided into several large,
thick plates that
– slowly move and change in size and shape.
• Plate boundaries are the sites of intense
geologic activity (e.g., earthquakes and
volcanoes).
Tectonic Plates
Practical Aspects of
Geology
Practical Aspects of Geology
• Natural Resources
– All manufactured objects
depend on Earth’s
resources
– Localized concentrations of
useful geological resources
are mined or extracted
– If it can’t be grown, it must
be mined
– Most resources are limited
in quantity and nonrenewable
Resource Extraction and
Environmental Protection
• Coal Mining
– Careless mining can release
acids into groundwater
Resource Extraction and Environmental Protection
• Petroleum Resources
– Removal,
transportation, and
waste removal can
damage the
environment.
Alaskan Pipeline
National Petroleum Reserve - Alaska
•
Completed in 1977
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1,250 km long
Final cost of $7.7 billion (estimated at $900 million)
Alaska provides as much as 20% of U.S. domestic oil
Built on permafrost – engineering problems
Earthquake prone region
–
Sections jointed to allow shifting of as much as 6 meters
without rupturing
Arctic National
Wildlife Refuge
Exxon Valdez Oil Spill - 1989
• 240,000 barrel of crude oil
spilled into Prince William
Sound
• Devastating effects on
wildlife and the fishing
industry
A “fix” to the energy crisis?
• North Slope ‘s Arctic National Wildlife Refuge
– Extreme points of view which are more emotional than scientific
• Any significant and potential oil field should be developed without
regard to environmental impact
• Any intrusion on an ecological environment is unacceptable
Geologic Hazards
Earthquakes
• Shaking can damage buildings and break utility
lines.
Undersea Earthquakes can Generate
Tsunamis
Sumatra earthquake and tsunami – December 26, 2004
Sumatra Tsunami
Marina beach in Madras, India
Commercial area of Banda Aceh,
Northeast Indonesia
Volcanoes
Mt. Pinatubo, Philippines
1991
Hawaii, USA
Mt. St. Helens, USA
1980
Mass Movement
Mudflows in Armero, Colombia was buried under 8 meters of mud
1985
Mass Movement
Floods
Wave Erosion
Earth’s Heat Engines
• Heat Engines convert
heat energy into
mechanical energy.
Heat energy is converted to
mechanical energy
Earth’s External Heat Engine
• Primary driver of
circulation in the
– atmosphere (weather)
– Hydrosphere (ocean
currents
• Controls weathering
of rocks at Earth’s
surface
Earth’s Internal Heat Engine
• Hot, buoyant material deep within Earth moves slowly
upward
• Denser material move downward
• Primary driver of
– Volcanism
– Tectonics
Earth Systems
• Earth has four major systems.
• Each system is shaped by a related set of
processes and parts.
• They are closely connected and interact
with one another.
• This means that a change in one system
can cause a change in another.
An Interdisciplinary Approach to
Studying Earth
• The way in which individual components of
land, water, air, and life forms are
connected must be understood.
• A system is
– Any size group of interacting parts that form a
complex whole to serve a function
– Most natural systems are driven by sources of
energy that move mater and/or energy from
one place to another.
Earth’s Four Spheres
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Earth is divided into four independent parts
Each loosely occupies a shell around Earth - This why they’re called spheres
The Geosphere
• The solid Earth
• The largest sphere
– Extends from the
surface to the center of
the planet
• Three principle regions
based on
compositional
differences
– Crust
– Mantle
– Core
The Atmosphere
• A very shallow layer of
gases
• 99% is within 30 km (20
mi) of Earth’s surface
• An integral part of our
planet
– Provides the air we breath
– Protects us from harmful
short-wave solar radiation
• Energy exchanges
between Earth’s surface
and the atmosphere and
space produce weather.
The Hydrosphere
• The collective mass of water found on, under, and above
Earth’s surface
• The hydrosphere includes . . .
Oceans
• Cover nearly 71% of Earth’s surface
• Average depth is 3,800 meters (12,500 ft.)
• Accounts for 97% of Earth’s water
Streams
Lakes
Glaciers
Ground Water
Clouds
Volume Comparisons
Volume of the
Entire Hydrosphere
Volume of the
Entire Atmosphere
The Biosphere
• Includes all life on Earth
• Most is concentrated near
Earth’s surface
Distribution of Earth’s Water
Geologic Time
“Nothing hurries geology”
- Mark Twain
What is Time?
• Time is how we sense and record
changes in the environment.
• It is our sense of one thing happening after
another.
• We need standards of time for the convenience
of everyday life.
Units of time
• As humans we think of time related to personal
experience.
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Seconds
Minutes
Hours
Month
Years
Decades
Centuries
Millenia
However, you will see that when we talk
about Earth history, even using a
millennium isn’t sufficient because
of Earth’s vast age.
Deep Time
• When we study history 200,
1,000 or even 2,000 years seems
like a long time.
• Geology involves vastly greater
amounts of time
– This is referred to as deep time.
Geologic Processes
• Most are slow but relentless
– Reflecting the pace at which the heat engines work
– It’s unlikely that a mountain will visibly change shape
or height during a human lifetime
Geologic Processes
• In a geologic time frame
– Most mountains are probably eroding “rapidly”
Uluru is a great block of uptilted sandstone in the heart of Australia's Outback.
This region may be the world's best-developed peneplain,
and Uluru its best-known monadnock.
To a geologist . . .
• “Rapidly” may mean within a few million
years.
• A “fast” process
– Started and completed within a few million
years.
– For example . . .
Rate of Plate Motion
• At a mid ocean ridge
– 1 cm/yr movement
– 100,000 years for the
seafloor to move 1,000
km (100,000 cm in one
km)
Some geologic processes do occur quickly
Mt. St. Helens
Landslides Occur Quickly
• Tully Valley landslide on April 27, 1993
• Occurred after heavy precipitation of
190 mm (7.5 in) during April in conjunction
with melting of a winter snowpack
Scale Model of Earth History
The Geologic Time Scale
• Earth history is subdivided into time units based
on:
– The fossil record
– Extinctions
The Geologic Time Scale
The “calendar” into which geologic events are placed.
Figure 1-03