easc116 introduction

Geology is a young science

Geology = study of solid EarthRoots are in observations of

natural world

Nicolaus Steno (1669)

1669: Nicolaus Steno

Originated three basic principles:

1) Superposition

- in series of layers, oldest layer is on bottom

Steno’s Basic Principles

2) Original Horizontality

- sediments (layers) are deposited parallel to Earth’s surface

- forces act on rx after they were deposited

Steno’s Basic Principles

3) Lateral Continuity- sediment deposited to the edge

of its depositional environment- rock layers continue laterally for

a distance

Lateral Continuity

Determined by field

mapping or drilling

Principle of Uniformitarianism

1787: James HuttonPhysical, chemical, & biologic

laws unchanged through time- forces which appear small can

produce features very largeEx: Colorado River and Grand

Canyon

Uniformitarianism

Important: Processes are the same, but the rates change

Ex: Earth’s harsh early atmosphere & lack of plants speeded erosion

Ex: Banded iron formations

Physical Geology

Studies:

1)Earth Materials- minerals- rocks

Physical Geology

Studies: - changes on

Earth’s surface

& interior

Physical Geology

2) dynamic forces that cause change (both external & internal)

THEME:

EARTH IS DYNAMIC!

(and)

Everything is connected

4 parts to Earth’s system:

1) Atmosphere - carbon dioxide (CO2)

- free oxygen (O2)

- water vapor (H2O)

4 parts to Earth’s system:

2) Hydrosphere – includes:

4 parts to Earth’s system:

3) Biosphere – all life

4) Geosphere – planet

Earth’s structure = crust, mantle, core

4 parts are interrelated:

Ex: Clear cutting a forest

Biosphere:

Atmosphere:

Geosphere:

Hydrosphere:

4 parts are interrelated:

Ex: Volcanic eruption

Biosphere:

Atmosphere:

Geosphere:

Hydrosphere:

Uniformitarianism

Important: Processes are the same, but the rates change

Ex: Earth’s harsh early atmosphere & lack of plants speeded erosion

Ex: Banded iron formations

All parts are interrelated:

Ex: building a dam

Biosphere:

Atmosphere:

Geosphere:

Hydrosphere:

Glen Canyon Dam

Science

Attempts to understand, explain, and predict events

- collects data to discover patterns in natural world

Geologists at Work

Tools of Geology

Rock Hammer

Maps

Detective Analogy

Geologists are solving a mystery

Scene of Clues Crime

the Crime Solved

Scientific Process

Ask a question:

Why doesn’t my #!*#*! car start?

1) Collect facts by observation or measurement

Gas gauge, lights, radio, etc.

Scientific Process

2) Explain how or why it happens(hypothesis)

Battery is dead3) Design experiment to test

validity of hypothesis Try to jump start battery

Scientific Process

4) Accept, modify, or reject hypothesis after extensive testing

Theory – well-tested framework that best explains the observations

Scientific Revolution

New information leads to a better explanation of observations

Occurs due to:a) new approach to the

question

b) new technology

Scientific Revolution in Geology

Continental Drift

1915:

Alfred Wegener

- hypothesized the supercontinent Pangaea (“all land”)

Pangaea

2 byo rx

Both 2 byo & ½ byo rx

Scientific Revolution

New information leads to a better explanation of observations

Occurs due to:a) new approach to the

question

b) new technology

WWII

New technology = fathometer-used to map ocean floor

topography

Harry Hess

1962:

Hypothesized sea-floor spreading

Plate dynamics

Hydrothermal Vents

Plate map

Plate Tectonics Theory

Plate – rigid slab of lithosphere

Plates move independently

Types of Plate Boundaries

1) Divergent – plates pull away from each other

- caused by magma rising to create new seafloor

- “sea-floor spreading”

Types of Plate Boundaries

2) Convergent – plates collide

Can be marked by:

a) deep-sea trenches

b) mountains

c) volcanic activity

Types of Plate Boundaries

3) Transform

- plates slide laterally

- characterized by shallow EQ’s

Ex: San Andreas Fault

Geologic Time

“Deep time”

Earth = 4.6 billion years old

Relative Dating – putting rocks/events in chronological order

1st, 2nd, 3rd, etc.

Geologic Time Scale

Paleozoic Era (“ancient life”)

“Age of Invertebrates”

- ended with largest mass extinction in Earth’s history

(over 90% organisms were extinct by 245 mya)

Geologic Time Scale

Mesozoic Era (“middle life”)

“Age of the Dinosaurs”

- ended with extinction of dinosaurs (66 mya)

Geologic Time Scale

Cenozoic Era (“recent life”)

“Age of Mammals”

Will the Cenozoic Era end?