Introduction Introduction Geology Ch Chapt apter 1 r 1 Geology - - PDF document

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Ch Chapt apter 1 r 1

Understanding Earth (Earth systems) A Dynamic and Evolving Planet

Introduction Introduction Geology

Geology is the study of the earth, a complex, integrated system of related parts, components, or sub- systems that interact in an organized fashion, affecting one another in various ways.

Introduction Introduction

The systems

• f the earth

include the:

– Atmosphere – Biosphere – Hydrosphere – Lithosphere – Mantle (plate tectonics) – Core (geo- dynamo & geomagnetics)

The interaction of these subsystems has resulted in a dynamically changing planet in which matter and energy are continuously recycled into different forms.

Introduction Introduction

Earth Systems Earth Systems

Climate system (how, why, etc)

• 1. Weather, complex, unable to predict with

accuracy beyond week or so

• 2. Climate = weather over time, general

predictions,

• 3. System driven by sun; interaction with
• cean/land, atmosphere, earth rotation/tilt,

etc, plus interference due pollution, volcanic dust, etc (geology)

Earth Systems Earth Systems

Plate Tectonics (theory/geological model)

• 1. Combines volcanism, earthquakes, shape
• f continents, seafloor surface, etc
• 2. Driven by convection within earth mantle

due to internal heat, radiation,

• 3. Affects lithosphere, crust & outer mantle

(depth to 100 km) and asthenosphere (plastic layer within mantle)

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Earth Systems Earth Systems

Plate Tectonic: Driving force similar to boiling pot of water The plate tectonics system The plate tectonics system: how does : how does the heat energy inside the Earth move the heat energy inside the Earth move and thus affect the crustal plates? and thus affect the crustal plates?

Convection causes hot w ater to rise… ...w here it cools, m oves laterally, sinks,… …w arm s, and rises again. Hot m atter from the m antle rises,… …causing plates to form and diverge. W here plates converge, a cooled plate is dragged under… …sinks, w arm s, and rises again.

Plate Plate

The The geodynamo geodynamo system system: rapid motion of : rapid motion of the liquid outer core stirs up electrical the liquid outer core stirs up electrical flow in the solid (iron) inner core flow in the solid (iron) inner core – – causing Earth causing Earth’ ’s magnetic field s magnetic field Geology is the study of the Earth.

Physical geology is concerned with the materials and processes which compose and

• perate on the surface of, and within, Earth.

Historical geology is concerned with the

• rigin and evolution of Earth's continents,
• ceans, atmosphere, and life.

What is geology?

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What is geology?

Geologists are employed in diverse occupations.

Principle occupations

include:

Mineral and energy resource exploration Solving environmental problems Predicting natural disasters

Geology and the Formulation of Theories What is a theory?

It is arrived at through the scientific method, which involves gathering and analyzing facts formulating hypotheses to explain the phenomenon testing the hypotheses and finally proposing a theory. The hypotheses is a tentative explanation. A scientific theory is a testable explanation for some natural phenomenon, that is supported by a large body

• f evidence.

Scientific method: Steps

1. Observation/Experimentation ->someone develops tentative explanation -> becomes hypothesis 2. Hypothesis -> presentation (publication or abstract/presentation verbally) to peers 3. Peers challenge hypothesis

• If passes challenge then several hypotheses may

form theory 4. Theory (-> presentation)

• Challenge to theory

5. Scientific model (combine theories with hypotheses)

Scientific method: Scientific method:

The scientific method The scientific method

in Geology in Geology

the goal: the goal: is to explain how the universe works is to explain how the universe works

How Does Geology Relate to the How Does Geology Relate to the Human Experience? Human Experience?

• Geology pervades our

everyday lives and is a part of many aspects of human experience, including the arts and literature.

• The range of

environmental problems and issues of concern to society require a basic understanding of geology.

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How does geology affect our daily How does geology affect our daily lives? lives?

• Natural Events
• Economics and Politics
• Our Role as Decision

makers

• Consumers and Citizens
• Sustainable

Development

Discussion: product source

Global Geologic and Environmental Global Geologic and Environmental Issues Facing Humankind Issues Facing Humankind

• Most scientists would

argue that

• verpopulation is the

greatest problem facing the world today.

• Increasingly large

numbers of people must be fed, housed, and clothed, with a minimal impact on the environment.

Global Geologic and Environmental Global Geologic and Environmental Issues Facing Humankind Issues Facing Humankind

• The greenhouse effect is the retention of heat in the

atmosphere, which results in an increase in the temperature of Earth’s surface and atmosphere, thus producing global warming.

Origin of the Universe Origin of the Universe

• Did it begin with a Big Bang?

– In the Big Bang theory, the universe began approx. 14 billion years ago (13.7 Ga). – At that time an extremely compressed, dense, hot body of matter exploded, began to expand and is now cooling

Origin of the Universe Origin of the Universe

How do we know? Evidence for the Big Bang:

– Evidence: universe is expanding from a central point.

• 1. Doppler effect:

the spectral line (wavelengths of galaxy light) shifts to red end (longer wavelength) due the expansion of galaxies.

Motion to left causes waves to have shorter wavelength on left and longer

• n right

Example: siren on car moving to left is higher pitch on left and lower

• n right side

Origin of the Universe Origin of the Universe

How do we know? Evidence for the Big Bang:

• 1. Doppler effect
• 2. Background

radiation: The entire universe has a pervasive and constant background radiation, thought to be the faint afterglow of the Big Bang.

• 1. Doppler effect: red & blue shift
• 2. Radiation so temperature is

2.7 degrees above absolute zero ( -273.0 C)

• r -270.3 C

where it should be at absolute zero

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Solar System: The nebular hypothesis (4.6 Solar System: The nebular hypothesis (4.6 Ga Ga) Immanuel Kent, German 1755 ) Immanuel Kent, German 1755

Summary Summary

1.

• 1. the sun forms (rotating cloud gas & dust,

the sun forms (rotating cloud gas & dust, compact, ignite, fusion =>proto compact, ignite, fusion =>proto-

• sun (early sun))

sun (early sun)) 2.

• 2. the planets form

the planets form

• planetesimals

planetesimals (hot gases cool to these, (hot gases cool to these, crash together to form terrestrial planets) crash together to form terrestrial planets)

• inner rocky planets (terrestrial)

inner rocky planets (terrestrial) V, M, E, M V, M, E, M

• outer
• uter jovian

jovian planets (gas & ice) planets (gas & ice) J, S, U, N J, S, U, N

Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of Solar system Origin of the solar system Origin of the solar system

Small bodies of the solar system Small bodies of the solar system

• Asteroids (between Mars & Jupiter,

Asteroids (between Mars & Jupiter, 300 with dia.>100km, 10,000 with 300 with dia.>100km, 10,000 with diameter>10km) diameter>10km)

• Meteorities

Meteorities – – small pieces of asteroids, small pieces of asteroids, probably similar formation, left probably similar formation, left overs

• vers
• Comets

Comets – – ice and dust, located in ice and dust, located in

• uter reaches of solar nebula
• uter reaches of solar nebula

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Our Solar System Our Solar System

Its Origin and Evolution

– The Solar System formed from a rotating cloud of interstellar matter about 4.6 billion years ago – This cloud, upon condensing, collapsed under the influence of gravity and flattened into a rotating disk. – The sun, planets, and moons formed within this disk.

Earth

Its Place in Our Solar System

Earth formed from a swirling eddy of nebular material 4.6 billion years ago, accreting as a solid body and soon thereafter differentiated into a layered planet during a period of internal heating.

Why Earth is a Dynamic and Evolving Planet

Earth has continuously changed during its 4.6 billion year existence as a result of interactions between its various subsystems and cycles.

Earth is composed of 3 concentric layers. Core Mantle Crust.

Why Earth is a Dynamic and Evolving Planet

The core consists of a small, solid inner region a larger, liquid, outer portion Composed of iron and a small amount of nickel.

The Core

Why Earth is a Dynamic and Evolving Planet Why Earth is a Dynamic and Evolving Planet

The mantle surrounds the core and is divided into: a solid lower mantle an asthenosphere that behaves plastically and flows slowly a solid upper mantle. Composed primarily of peridotite, an igneous rock made of olivine.

The Mantle

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Why Earth is a Dynamic and Evolving Planet

The outermost layer, the crust, is divided into: thick continental crust thin oceanic crust

The Crust

Why Earth is a Dynamic and Evolving Planet

The Asthenosphere

Surrounds the lower mantle Behaves plastically and slowly flows Partial melting in the asthenosphere generates magma (molten rock) that rises to the earth’s surface.

Why Earth is a Dynamic and Evolving Planet

The Lithosphere

The crust and upper mantle make up the lithosphere which forms the solid outer layers of the Earth.

Why Earth is a Dynamic and Evolving Planet

Plate Tectonic Theory

The lithosphere is composed of rigid plates that diverge, converge, or slide sideways past one another as they move over the asthenosphere

Why Earth is a Dynamic and Evolving Planet

Plate Tectonic Theory

Why Earth is a Dynamic and Evolving Planet

Plate Tectonic Theory

Volcanoes and earthquakes occur at the boundaries between the plates.

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Why Earth is a Dynamic and Evolving Planet

Plate Tectonic Theory

Plate tectonic theory is a unifying explanation for many geologic features and events, helping us understand the composition and internal processes of Earth on a global scale.

The Rock Cycle

A rock is a solid aggregate of one or more minerals, as well as non-crystalline matter such as natural glass or

• rganic material like coal.

There are three major groups of rocks

Igneous Sedimentary Metamorphic

The Rock Cycle

Igneous Rocks form from the crystallization

• f magma as it cools or the consolidation of

volcanic ejecta.

Intrusive igneous rock crystallizes beneath the earth’s surface. Extrusive igneous rock crystallizes and cools at the earth’s surface. At times it cools so fast that it forms a glass or ash.

Granite Granite Intrusive Igneous Rock Intrusive Igneous Rock Basalt Basalt Extrusive Igneous Rock Extrusive Igneous Rock

The Rock Cycle

Sedimentary Rocks are typically deposited in layers formed from:

rock/mineral fragments precipitation of minerals from solution the compaction of plant and animal remains.

Lim estone Lim estone Precipitation from seaw ater Precipitation from seaw ater Conglom erate Conglom erate Form s from river gravels Form s from river gravels

The Rock Cycle

Metamorphic Rocks form from alteration of

• ther rocks, usually by:

Heat Pressure Chemically active fluids

Quartzite Quartzite Gneiss Gneiss

The Rock Cycle

The rock cycle illustrates the interactions between Earth’s internal and external processes and how the three rock groups are interrelated.

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The Rock Cycle

How are the rock cycle and plate tectonics related?

Plate movement is the driving mechanism of the rock cycle. Plate inter- action determines, to some extent, which of the three rock groups will form.

Organic Evolution and the History of Life

The theory of organic evolution states:

that all living things are related and have descended with modification from organisms living in the past. Charles Darwin proposed that the mechanism of natural selection results in survival reproductive age

• f those organisms best suited to their environment.

Fossils, the remains of once-living organisms provide the evidence for evolution and a history of life before humans.

Organic Evolution and Plate Tectonics

Together the theories of plate tectonics and organic evolution have changed the way we view

• ur planet.

Geologic Time

An appreciation of the immensity of geologic time is central to understanding the evolution of the Earth and its’ life.

Geologic time differs from the human perspective of time Earth goes through cycles of much longer duration than the human perspective of time The immense span of time encompassed by the Earth's existence and geological processes sets geology apart The geologic time scale is the calendar that geologists use to date past events in Earth’s history.

Geologic Time and Uniformitarianism

Uniformitarianism forms a cornerstone of geology. It is a fundamental tenet of geology. This principle states that the laws of nature have remained unchanged through time and thus, that the processes observed today have also operated in the past, though possibly at different rates. Therefore, to understand and interpret geologic events from evidence preserved in rocks, geologists must first understand present-day processes in rocks.

How does the study of geology benefit us?

Understanding how the Earth’s subsystems work will help ensure the survival of the human species. It will help us to understand how our actions affect the delicate balance between these systems.

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