Environmental Geology – Plate...

8
1 Environmental Geology – Plate tectonics Plate tectonics Reading: This week: Ch 3 Next week: Ch 4 Internal processes: Environmental Geology – Plate tectonics The Earth’s magnet Magnetic dip at equator: 0 (horizontal) at pole: 90 deg (vertical) tells us about the latitude when the rooks cooled Magnetic azimuth the compass needle points north Normal polarity Environmental Geology – Plate tectonics The Earth’s magnet Magnetic dip at equator: 0 (horizontal) at pole: 90 deg (vertical) tells us about the latitude when the rooks cooled Magnetic azimuth the compass needle points south Reverse polarity Environmental Geology – Plate tectonics Reconstructing plate motion Plate tectonics: The magnetic tape recorder: Given the oceanic record we can wind back the plates to see how the plates have been moving. This shows us how Pangaea broke up.

Transcript of Environmental Geology – Plate...

Page 1: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

1

Environmental Geology – Plate tectonics

Plate tectonics

Reading: This week: Ch 3Next week: Ch 4

Internal processes:

Environmental Geology – Plate tectonics

The Earth’s magnet

Magnetic dip

• at equator: 0 (horizontal)

• at pole: 90 deg (vertical)

tells us about the latitude when the rooks cooled

Magnetic azimuth

• the compass needle points north

Normal polarity

Environmental Geology – Plate tectonics

The Earth’s magnet

Magnetic dip

• at equator: 0 (horizontal)

• at pole: 90 deg (vertical)

tells us about the latitude when the rooks cooled

Magnetic azimuth

• the compass needle points south

Reverse polarity

Environmental Geology – Plate tectonics

Reconstructing plate motion

Plate tectonics:

The magnetic tape recorder:

Given the oceanic record we can wind back the plates to see how the plates have been moving.

This shows us how Pangaea broke up.

Page 2: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

2

Environmental Geology – Plate tectonics

Continental magnetizationPlate tectonics:

Environmental Geology – Plate tectonics

Plate motion further back in timePlate tectonics:

Environmental Geology – Plate tectonics

The formation of PangaeaPlate tectonics:

When we add the continental plate motion recoded we can extend plate reconstruction back beyond 200Ma

i.e. prior to the break-up of Pangaea

QUESTION

Environmental Geology – Plate tectonics

Properties of geological materialsEarth’s interior:

How can plates move across the Earth’s surface?

The Earth is not a rigid solid, but a plastic solid.

Page 3: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

3

Environmental Geology – Plate tectonics

Properties of geological materialsEarth’s interior:

How can plates move across the Earth’s surface?

The Earth is not a rigid solid, but a plastic solid.

Brittle failure: Rupture

Plastic deformation: Ductile flow

Environmental Geology – Plate tectonics

An overviewEarth’s interior:

Environmental Geology – Plate tectonics

Categories of plate boundariesDivergent

• Established mid-ocean ridge• New rift zone, new ocean

Transform• Along mid-ocean ridges• Across continents

Convergent• Ocean – continent • Ocean – ocean • Continent – continent

Plate tectonics:

Environmental Geology – Plate tectonics

Categories of plate boundaries

Divergent• Established mid-ocean ridge Mid-Atlantic Ridge• New rift zone, new ocean East African Rift

Transform• Along mid-ocean ridges Fracture Zones e.g. south Pacific• Across continents San Andreas Fault

Convergent• Ocean – continent Off west coast of South America• Ocean – ocean Japan Trench, western Pacific• Continent – continent Himalaya

Plate tectonics:

Page 4: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

4

Environmental Geology – Plate tectonics

Mid-Atlantic RidgeDivergent boundaries:

Environmental Geology – Plate tectonics

Mid-ocean ridge resourcesDivergent boundaries:

Black smokers produce rich mineral deposits …at 2.5 km depth

Environmental Geology – Plate tectonics

The East African Rift and Red Sea

Divergent boundaries:

Environmental Geology – Plate tectonics

The Red SeaDivergent plate boundaries:

Page 5: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

5

Environmental Geology – Plate tectonics

The continental rifting process provides the right environment for oil formation within continental margin

sediments

Divergent plate boundaries:

Oil at the continental margin

Environmental Geology – Plate tectonics

Ocean transformsTransform plate boundaries:

Mid-ocean ridges are

offset by ocean

transforms:

Fracture Zones

Ocean bathymetry map

Environmental Geology – Plate tectonics

Ocean transformsTransform plate boundaries:

Environmental Geology – Plate tectonics

San Andreas FaultTransform plate boundary:

Page 6: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

6

Environmental Geology – Plate tectonics

San Andreas FaultTransform plate boundary:

Environmental Geology – Plate tectonics

Different typesConvergent plate boundaries:

Environmental Geology – Plate tectonics

South AmericaConvergent plate boundaries:

Environmental Geology – Plate tectonics

Different typesConvergent plate boundaries:

Page 7: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

7

Environmental Geology – Plate tectonics

India and Asia – the HimalayaConvergent plate boundaries:

QUESTION

Environmental Geology – Plate tectonics

The Ring of Fire

Refers to the concentration of earthquakes and volcanoes around the Pacific rim.

Environmental Geology – Plate tectonics

Determining plate velocitiesPlate tectonics:

1. Magnetic stripes on the ocean floor

2. Hotspot tracks record plate motion

Environmental Geology – Plate tectonics

Hotspot tracksPlate tectonics:

Strings of volcanic ocean islands recording the motion of the plate

Hawaiian chain The formation process

Page 8: Environmental Geology – Plate tectonicsseismo.berkeley.edu/.../Lectures/L05_PlateTectonics_4.pdf · 2 Environmental Geology – Plate tectonics Continental magnetization Plate tectonics:

8

Environmental Geology – Plate tectonics

Global hotspot tracksPlate tectonics:

Environmental Geology – Plate tectonics

Plate velocitiesPlate tectonics:

Environmental Geology – Plate tectonics

The unifying theoryPlate tectonics:

Plate tectonics: Recognizes that rigid plates are moving across the Earth’s surface.

A unifying theory: A single theory that explains a large body of evidence.

Other examples:

Physics – theory of relativityChemistry – nature of a chemical bondAstrophysics – the Big BangBiology – DNAGeology – plate tectonics