Introducing GeologyIntroducing Geology

What is Geology?What is Geology?

• Geology - the scientific study of Earth.– Physical Geology is the study of:

• Earth Materials– Minerals

– Rocks

GeologyGeology• 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 ProcessesSurface Processes• Erosion - Movement of Weathered Earth

materials on Earth’s surface

Surface Processes (cont.)Surface Processes (cont.)• Uplift

– Volcanic and/or tectonic forces build crust up above sea level

UpliftUplift

– Removal of material by erosion allows isostatic uplift of underlying continental rocks.

IsostasyIsostasy

Figure 1-16A

• Archimedes’ Principle– Every floating object is pushed upward by a buoyant

force that is• Equal to the weight of the displaced fluid

Isostasy (Greek for “equal standing”)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.)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 Structure and Processes of Earth’s InteriorEarth’s Interior

Gravity Meter

Magnetometer

Seismographs

TectonicsTectonics

• The study of the origin and arrangement of Earth’s structural features which include– Folds and faults but also – Continents– Mountains– Earthquake regions.

Plate TectonicsPlate 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 PlatesTectonic Plates

Practical Aspects of Practical Aspects of GeologyGeology

Practical Aspects of GeologyPractical 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 non-renewable

Resource Extraction and Resource Extraction and Environmental ProtectionEnvironmental Protection

• Coal Mining– Careless mining can release

acids into groundwater

Resource Extraction and Environmental ProtectionResource Extraction and Environmental Protection

• Petroleum Resources– Removal,

transportation, and waste removal can damage the environment.

Alaskan PipelineAlaskan Pipeline

• Completed in 1977– 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

National Petroleum Reserve - Alaska

Arctic NationalWildlife Refuge

Exxon Valdez Oil Spill - 1989Exxon 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?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 HazardsGeologic Hazards

EarthquakesEarthquakes• Shaking can damage buildings and break utility

lines.

Undersea Earthquakes can Generate Undersea Earthquakes can Generate TsunamisTsunamis

Sumatra earthquake and tsunami – December 26, 2004

Sumatra TsunamiSumatra Tsunami

Marina beach in Madras, India

Commercial area of Banda Aceh, Northeast Indonesia

VolcanoesVolcanoes

Mt. St. Helens, USA1980

Hawaii, USA

Mt. Pinatubo, Philippines1991

Mass MovementMass Movement

Mudflows in Armero, Colombia was buried under 8 meters of mud1985

Mass MovementMass Movement

FloodsFloods

Wave ErosionWave Erosion

Earth’s Heat EnginesEarth’s Heat Engines

• Heat Engines convert heat energy into mechanical energy.

Heat energy is converted tomechanical energy

Earth’s External Heat EngineEarth’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 EngineEarth’s Internal Heat Engine

• Hot, buoyant material deep within Earth moves slowly upward

• Denser material move downward• Primary driver of

– Volcanism– Tectonics

Earth SystemsEarth 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 An Interdisciplinary Approach to Studying EarthStudying 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 SpheresEarth’s Four Spheres

• Earth is divided into four independent parts• Each loosely occupies a shell around Earth - This why they’re called spheres

The GeosphereThe 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 AtmosphereThe 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 HydrosphereThe Hydrosphere

• The collective mass of water found on, under, and above Earth’s surface

• The hydrosphere includes . . .

OceansOceans

• Cover nearly 71% of Earth’s surface• Average depth is 3,800 meters (12,500 ft.)• Accounts for 97% of Earth’s water

StreamsStreams

LakesLakes

GlaciersGlaciers

Ground WaterGround Water

CloudsClouds

Volume ComparisonsVolume ComparisonsVolume of the

Entire HydrosphereVolume of the

Entire Atmosphere

The BiosphereThe Biosphere• Includes all life on Earth• Most is concentrated near

Earth’s surface

Distribution of Earth’s WaterDistribution of Earth’s Water

Geologic TimeGeologic Time

““Nothing hurries geologyNothing hurries geology””

- Mark Twain- Mark Twain

What is Time?What is Time?

• It is our sense of one thing happening after another.

• We need standards of time for the convenience of everyday life.

• Time is how we sense and record changes in the environment.

Units of timeUnits of time

• As humans we think of time related to personal experience.– 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 TimeDeep 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 ProcessesGeologic 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 ProcessesGeologic 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 . . .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 MotionRate 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 Some geologic processes do occur quickly Mt. St. Helens

Landslides Occur QuicklyLandslides 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 HistoryScale Model of Earth History

The Geologic Time ScaleThe Geologic Time Scale

• Earth history is subdivided into time units based on:– The fossil record– Extinctions

The Geologic Time ScaleThe Geologic Time ScaleThe “calendar” into which geologic events are placed.The “calendar” into which geologic events are placed.

Figure 1-03