GEOLOGIC ERAS AND

PLATE TECTONICS

Planet Earth

1. Geologic History

2. Earth’s Interior

3. Tectonic Plates

Geologic History

• Precambrian Era

• 4.6 billion years ago until

570 million years

FaultAncient Sea

Igneous Rockmagma Ancient Sea

Sediments

1) Mountain building

2) erosion

-Original Canadian Shield

-First single and multi-celled organisms

Geologic History

• Paleozoic Era

• 543 to 248 Million Years Ago

Igneous Rock

Erosion

SedimentsSediments Very Old

Lower layers changed into rock

Interior Plains

Appalachian Mountains

1) No Mountains2) Sedimentary Rock uplift

3) Sedimentary RockFolding/uplift

-NA covered by shallow seas-Appalachians formed-1st plants and animals appear on land

Geologic History

• Mesozoic Era

• 248 to 65 Million Years Ago

Mountains Forming

Igneous Rock

1) CDN Shield

5) GLSLL2) AppalachianMTNS

“old eroded”

3) Western Cordillera4) Interior Plains“folding young”

oil

-Formation of Rocky Mountains Begins-Reptiles and Dinosaurs-1st birds and mammals

Geologic History

• Cenozoic Era

• 65 million years to present (US!)

Mountains Forming

Igneous RockHeat

Volcanic Activity

Rockies 4) INTERIOR PLAINS 1) CANADIAN

SHIELD

3) APPALACHIAN

ATLANTIC OCEAN

2) GLSLL

CoastalMountains

5) WESTERN CORDILLERA

-Ice sheets cover most of NA-Continents take on present shape-Modern forms of life evolve

Earth’s Interior

Crust- 8-64 km thick- cold & fragile- Granite and Basalt

Mantle- 1800 km thick- hot & molten- Magnesium and Silicon

Outer Core- 2000 km thick- 3 - 4000°C- liquid Nickel and Iron

Inner Core- 1400 km thick- 5 - 6000°C- solid Nickel and Iron

Air

Land

Water

LITHOSPHERE

HYDROSPHERE ATMOSPHERE

Plate Tectonics - Continental Drift

Plate Tectonics - Continental Drift

Plate Tectonics - Continental Drift

Antarctica

THE CONTINENTS TODAY

HMMMM

• Close examination of a globe often results in the observation that most of the continents seem to fit together like a puzzle: the west African coastline seems to snuggle nicely into the east coast of South America and the Caribbean sea; and a similar fit appears across the Pacific.

PANGAEA

• 1912 Alfred Wegener (1880-1930)

• proposed that the continents were once compressed into a single large continent which he called Pangaea (meaning "all lands"),

• believed that Pangaea was intact until about 300 million years ago, when it began to break up and drift apart.

FOUR MAIN PIECES OF EVIDENCE

• 1.

Wegener noted the jigsaw fit of South America and Africa, especially, but also elsewhere

PROOF CONTINUED

2. He found fossils that were the same on both continents. After a certain period, the fossils begin to evolve differently on the different continents.

3. He found that on both sides of the Atlantic, mountains were the same both in terms of age and structure.

4. He found that ice sheets covered parts of Africa, India, Australia and South America 250 million years ago. How could this happen in places that are so warm today?

PROBLEM

• Wegener's hypothesis of continental drift did NOT explain how the continents could drift across the earth's surface.

• ….thus, the theory of PLATE TECTONICS!NOT until the the 1960s

• Earth’s outer shell made up of 20 plates• They move over a weak layer of hot rock which flows like

slow-moving plastic• Unequal distribution of heat within the earth causes

convection currents to move the plates

Plate Tectonics Map

PLATE TECTONICS

• THERE ARE THREE BASIC PLATE MOVEMENTS

• 1. DIVERGENT

• where the plates move apart

• new magma wells up to the surface forming new crust

• the Mid-Atlantic ridge is a prime example.

MID-ATLANTIC RIDGE

2. CONVERGENT

• two plates come together

• one plate subducts (goes under) the other plate, creating a subduction zone

• the crust at the leading edge of the subducting plate melts back into the mantle

• 3 different types of convergent boundaries

MID-OCEANIC CONVERGENCE

B. Convergence Zone: Oceanic Crust and Continental Crust

CONTINENTAL-CONTINENTAL

Accumulated material melts as it goes down into the mantle.

Rises back up as liquid rock.Creates volcanoes and volcanic islands

http://en.wikipedia.org/wiki/Mount_St._Helens

3. TRANSFORM BOUNDARIES

• two plates slide past each other• this can create tremendous friction, which may be

eventually released in the form of violent earthquakes

• the San Andreas Fault is a transform boundary

SAN ANDREAS FAULTCALIFORNIA

Plate Tectonics Sliding

Plate Tectonics Sliding

• Less than 3.5 Generally not felt, but recorded.• 3.5-5.4 Often felt, but rarely causes damage.• Under 6.0 At most slight damage to well-

designed buildings.• 6.1-6.9 Can be destructive in areas up to about

100 kilometers across.• 7.0-7.9 Major earthquake. Can cause serious

damage over larger areas.• 8 or greater Great earthquake. Can cause serious

damage in areas several hundred kilometers across.

Tectonic setting of western British Columbia and Washington state. The oceanic Juan de Fuca plate is moving beneath the continental North America plate at a rate of about 4 cm/year. Earthquakes occur along parts of the boundary between the two plates.

This map, which shows 20th-century earthquakes in red, illustrates how they cluster on the edges of the major tectonic plates (outlined in yellow).

SUMMARY

Theory of continental drift and evidence to support it. (Pangea!)

Plate tectonics: how plates move (convection currents)Different movements of plates, geologic processes and

associated landformsDiverging: ridges/volcanoes

Converging: trenches, mountains, island arcsSubducting: same as above

Slipping/Transform: faults and earthquakesEarthquakes and Volcanoes: along major tectonic

plate boundaries