Geology Chapter 1 summary and overview

8/11/2019 Geology Chapter 1 summary and overview

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Geology as a Science

Geology at first was an observational science

People would see a geologic curiosity and describe it Later, people would attempt to explain it

Modern geology combines observation and laboratory activities(measurements and calculations) to explain natural phenomena

Geology has grown rapidly into an analytical science Experiments must consider changes in temperature, pressure, stress, chemical

parameters, and time

Not just a descriptive science, but a more quantitative and moreinterdisciplinary science through time

Starting materials that form rocks and minerals often are completely changedduring the course of time

Geology is an environmental science Rocks record how earth has changed over time

Recognition and mitigation of natural hazards

Scientific MethodA means to discover basic scientific principles

Starting Pointa set of observations and/or a body of data from measurements ofphenomena and/or experiments

Hypothesisis formed to explain the observations or data

Conceptual framework or model is developed

Multiple explanations or equations developed

Must be testable and test must be reproducible

Proof of a hypothesis is sought as well as evidence to disprove it

Test the hypothesis repeatedly and systematically

Make set of predictions and perform series of experiments

Theoryformed as accepted explanation for an observation or set of data

Hypothesis becomes a theory only after extensive testing of the hypothesis


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Theory versus Hypothesis

Theoryaccepted explanation

Must be a well tested model

Is subject of considerable investigation and data collection that is required to

evaluate it

A hypothesis is elevated to a theory only after extensive debate and

experimentation

Geology and the Scientific MethodGeology has problems that other sciences do not!

Problems with size

A volcano is huge!

A river is not easily contained within a laboratory

Plate Tectonics involves the whole Earth

Problems with time

Geologic processes take millions of years to complete

Geologists are limited by human time (years to decades)

Problems with resolution of data

New technology and procedures often impact, or challenge, old theories

We can see more details now than a century ago


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Why Environmental Geology? Environmental geology explores the many and varied interactions between

humans and geologic environments

Earth is a dangerous place!

Earthquakes and Volcanoes

Floods, Mass wasting, and Soil erosion

Global Warming

Quest for more energy

Pollution and Storage of toxic waste

Find and manage fresh water

Find new resources (they are limited)

Remediate sites of mineral extraction


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Population Growth

Population has experienced exponential growth:

Possibly 9 billion people by 2050

Slow population growth up until mid-19thcentury Life expectancy has increased

Birth rates have greatly exceeded mortality rates

People are more mobile and can live anywhere

New perils will confront us because of our increasing population

Limited exploitation of new sources of natural resources

Growing demand by third world countries wanting to become first worldcountries


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Impacts of the Human Population

Rapid growth of humans results in problems obtaining an adequate food supply

Expected problems:

Water supply for irrigation, drinking, and industry

Farmland to produce crops to feed a hungry earth

Food production is an energy-intensive business

Supply of energy and minerals for our material based lifestyle

Pollution of air, land, and water pursuing

Population distribution by region in 2002 with

projection to the year 2050


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Global population density; the darker the shading, thehigher the population density.

Impacts of the Human PopulationHow do we resolve the issues?What are the consequences because of the growth of the human population?

Energy and natural resources are finite supplies on earth

Where do we find more?

Water supplies have been exhausted in many places

Where do we find more? How to treat waste water?

Croplands are replaced by homes and cities

Where can we grow croplands?

Waste, the products of our life style, must be put somewhere

Where do we put it and at what cost? How to recycle it?

Carrying Capacity, its ability to sustain its population at a basic, healthy,moderately comfortable standard of living

Have we exceeded it?

Global Warming, the activity of billions of people is impacting the climate ofearth

Can we reverse it?


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An Overview of Our Planetary Environment

Chapter 1

The solar system formed over 4.5 billion

years ago. The earth is unique among the

planets in its chemical composition,

abundant surface water, and oxygen-rich

atmosphere

The interaction between geologic

environments and our 6 million human

beings reshapes our planet

Image collage from NASA/JPL

Earth in space and time

Big Bang, the origin of todays universe

The Big Bang Theoryis the dominant scientific theory about the origin ofthe universe. Although the Big Bang Theory is widely accepted, it probablywill never be proved.

According to the big bang, the universe was created around 13.7 billionyears ago from a cosmic explosion that expulsed matter and in alldirections.


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Stars formed from the debris of the Big Bang. Local high concentrations ofmass were collected together by gravity and formed stars and planets.

The sun and its system of circling nine planets formed from a rotating cloudof gas and dust.

Most of the mass of the cloud coalesced to form the sun. Dust condensedfrom the gases remaining in the flattened cloud, and the dust clumped intoplanets.

astro.unl.edu

The compositions of the planets formed depended largely on how near theywere to the hot sun.

The nearest planets to the sun contained mainly metallic iron, a few veryhigh temperature minerals, and little water or gas. Farther from the sun, theplanets incorporated much larger amounts of low temperature minerals,liquid water, and condensed gases.

A series of planets with a variety of compositions was born.



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The planetary densities are consistent with a higher metal and rock content in the

four planets closest to the sun and a much larger proportion of ice and gas in the

planets farther from the sun.


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Third planet from the Sun

around 4.5 billion years old

Mean temperature 15 o C, not too hot or cold

Eight chemically distinct planets in our Solar System

Four rocky and metallic inner planets

Inner-most planets very hot (nearest the Sun)

Four gaseous outer planets

Outer planets very cold

Ninth planet, Pluto, is not considered a planet

Universe is over 13.7 billion years old


The planets of the solarsystem have different

composition and physical

properties


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Solar System

About 4.5 billion years ago, out of a swirling mass of gas and dust, evolved asystem of varied planets hurtling around a nuclear-powered star -- thesystem is our solar system.

Formed after the universe

Planets revolve around Sun

One complete trip for Earth equals one year

Earth at 23.5otilt from the vertical

Hemispheres of the Earth do not receive equal solar energy year round

Because of the tilt

Produces seasons

Earthcontinuous change

Early Eartha barren world with a cratered surface

lacked oceans

Lacked atmosphere

Earth heated up and was molten

Earth was target of many impacts

Asteroids Dust Particles

Meteors

Comets


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As cooling progressed, dense materials, such as metallic iron, would sinktoward the middle of the earth while lighter, low-density minerals

crystallized and floated out toward the surface.

Process: Differentiation of this world developed compositional zones

Central core:dense and hot

Composed of nickel (Ni) and iron (Fe)

Mantle: thick zone that surrounds the core

Composed of ultramafic and mafic rocks and magma

Heat from core escapes by convective circulation

Crust: chemically different from core or mantle

Two types of crust: Oceanic (mafic) and Crustal (felsic)

Water and atmospheric gases interact only with outermost crust

Earthcontinuous change

A chemically differentiated earth


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Table 1.02

Early Atmosphere The heating and subsequent differentiation of the early earth led to theformation of the atmosphere and oceans.

Many minerals that contained water or gases in their crystals released themduring the heating and melting, and as the earths surface cooled, the water

could condense to form the oceans and gases form the atmosphere.

Chemically different than today

No modern pollution

Lacked free oxygen (O2)

Dominated by nitrogen (N) and carbon dioxide (CO2)

Minor amounts of other gases:

Methane (CH4)

Ammonia (NH3)

Sulfur gases


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The geologic spiral

First Life on earth

Early atmosphere required modification before life could evolve

Single-celled blue-green algae flourished first

Abundant oxygen was required for other life

Photosynthesis by algae produced oxygen

Sunlight energized a chemical reaction in algae

Food was produced from CO2 Oxygen given off as a by-product

Oxygen accumulated in the atmosphere

Life for oxygen meant breathing organisms could evolve


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Life Evolves on Earth

Last 500 million years

Vertebrates appeared about 500 millionyears ago

Land plants appeared about 400 millionyears ago

Insects developed about 300 millionyears ago

Dinosaurs appeared about 230 millionyears ago

Birds appeared about 150 millionyears ago

Mammals and birds well established by 100 millionyears ago

Primitive human (hominids) beings appeared by 2 to 3 millionyears ago

Modern humans (homo sapiens) appear during last 20,000years

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Geology Chapter 1 summary and overview