dynamic earth

The Earth’s Interior

The Earth’s InteriorFour Layers (see page 10 of Ref Tables)Inner Core: solid, dense, 6,000º C, Iron and NickelOuter Core: Liquid, dense, 3,700º-5,500ºC (increases with depth), Iron and NickelMantle: Solid, minerals rich in Fe, Si, Ma, 1,500º - 3,200º CCrust: upper layer, rigid, lighter rock, <1,000ºC

The Earth’s InteriorSome terms to know:Asthenosphere: Upper layer of the mantle, may act in a semi-fluid (plastic) mannerMoho (Mohorovicic Discontinuity): The boundary between the mantle and the crustLithosphere: Consists of the crust and the rigid upper mantle

The Earth’s Interior

Where is the crust thickest?Mountain Ranges.Where is the crust thinnest?

The Ocean Floor.

The Earth’s Interior

Why is the core so hot?Still retains heat from original formation.Radioactive materials releasing energy as they decay.Increased pressure from above.

The Earth’s InteriorWhat happens to rock density, going from the crust to the core?It increases.What happens to temperature, going from the crust to the core?It increases.What happens to pressure, going from the crust to the core?It increases.

Continental Drift and the Origin of Plate

Tectonics

Wegener’s Map showing the breakup of Pangea

See Reference TablePage 9

Note how they fit together

I.The Theory of Plate Tectonics :

The Earth’s lithosphere is made of a number of solid pieces, called __________ which move in relation to each other.

plates

These plates are “riding”ona more “plastic molten” layer below

These plates are “riding”on

a more “plastic molten” layer below

This plastic molten layer of magma is called the:

asthenosphere

1. Theory of Continental Drift

A. Proposed by _______ ________ in 1915. It stated that the earth’s continents separated and collided as they have moved over the surface of the Earth for millions of years.

Alfred Wegener

Alfred Wegener (1880-1930)Geographer and Polar Explorer

B. Wegener’s evidence for his his theory:1. When you line up __________ and _________ they fit like a puzzle.

S.AmericaAfrica

2. __________ species have been found on widely separated parts of the earth.

Fossil

3. Permian fossils are very similar in widely separated continents

Cynognathus

Lystrosaurus

Mt. SirusAntarctica•Lystrosaurus beds

Mesosaurus

3. _____________ and ______________ have a good match of ancient continental rocks and tectonic _________ and _________ structures.

S. AmericaAfrica

faultfold

4. Some mountain chains appear to be continuous from____________ to______________

continentcontinent

5. Evidence of _________ climatesdifferent from present.

ancient

Ex.Finding coal beds which indicate tropical climates

Technology developed during WWIISonar - image the deep ocean using reflected sound.Magnetometer - detect faint magnetic fields.Developed to search for U-boats

World War IISubmarine warfare

Harry Hess

• Geologist at Princeton U.

• 1962 publishes “geopoetry.”

• Sea floor spreading hypothesis.

• Suggested that the ocean floor itself might be moving.

Cold WarNuclear Submarines

SSN Nautilus•1st nuclear powered submarine

Mid-ocean ridge

6. Rocks of the ocean basins are _________ than continental rocks.

younger

II. Ocean Floor Spreading:

Further evidence of horizontal movement of earth’s crust:A. The ocean floor has a system of submerged mountain ranges called ______________________Mid-Ocean Ridges

Material from deep within the earth comes to the surface at the ___________________ where it spreads apart to make ________________.

Ocean ridges

New ocean crust

Sea floor spreading

B. The two major pieces of evidence are: Age of igneous ocean material

1.

2. Reversal of magnetic polarity

When rock hardened it kept the alignment forming a permanent record of the ___________________ of the earth at that time.

Magnetic field

N

S

N

S

N

SMagnetic polarity reversal

Rocks found farther from the ridges have a _____________ magnetic polarity. Parallel stripes of ________________ on either side of these ridges preserve the record of many ____________ of the earth’s magnetic field.

reversed

magnetism

reversals

Measuring the Age of the Ocean Floor

1968, establishment of the Deep Sea Drilling Project (DSDP).Specially outfitted ship for drilling into the ocean floor and retrieving rock samples.Sediment layers and igneous rock dated to reveal the age of the ocean floor in different places.

Deep Sea Drilling Project ship - Glomar Challenger

C. The _______ _________ (basaltic) igneous rocks of the crust near the ocean ridges are covered with a thin layer of ____________.

darkdense

sediment

This is evidence that the earth’s crust is very ___________ near the ridges.

young

The oldest parts of the ocean crust are found far from the ___________ ridges and near the _______________

ocean

continents

Acceptance of Sea Floor Spreading (Plate Tectonics)1970’s - rapid confirmation of

remaining predictions and acceptance of the basic theory by most geologists.1980’s - Plate Tectonics becomes the dominant paradigm in geology.1990’s - Development of a detailed plate tectonic history of the last 700 million years.

Lesson 2

Lithospheric Plates ___________ in size and are made up of a

combination of___________ crust and______________ crust

vary

oceaniccontinental

Three kinds of plate motion occur at plate boundaries:

1. _____________________

2. _____________________

3. _____________________

convergent

divergent

transform

Aerial view of the San Andreas fault slicing through the Carrizo Plain in the Temblor Range east of the city of San Luis Obispo. (Photograph by Robert E. Wallace, USGS.)

1a.When ocean collides with continent the_________ocean plate dives down under or ____________ into the mantle forming a ___________________

denser

subducts

Subduction zone

Oceanic-Continental Convergence

Ex. Andes in S.America

1b.When two ocean plates converge the _______ ___________ocean plate will __________ forming an ____________ ________

older

subductislandarc

denser

Oceanic-Oceanic ConvergenceEx. Indonesia, Phillippines,Japan & Aleutians

Called SUBDUCTION

Continent-Oceanic Crust Collision

1c.When two continental plates converge the edges of _______ are crumpled up forming _________________________

both

mountainsfolded

Continental-Continental Convergence Ex. Himalayas

Himalayas

2.At ____________ plate boundaries, the plates move ___________ and ________ flows up forming parallel ridges made of _________________ __________

divergent

magma

newigneous

apart

rock

Divergent Plate BoundaryEx. Mid-Atlantic Ridge

Iceland has a divergent plate boundary running through its middle

Iceland: An example of continental rifting

3. At ____________ plate boundaries, the plates move ________ each other causing shallow _____________ _______________

transform

earth

past

quakes

Transform Plate Boundary

Ex. San Andreas Fault of California

core

III. MANTLE CONVECTION CELLS:

These plates are “riding”ona more “plastic molten” layer below

III. MANTLE CONVECTION CELLS:

The evidence shows that approximately _______ million years ago, the major continents were _______________

200

connected

And since that time they have been ___________separating

A convection cell is a stream of heated material that is moving because of _________ DENSITY DIFFERENCES

These convection cells exist in part of the mantle called the _______________

ASTHENOSPHERE

asthenosphere

The two sources of this heat are:1.

2.

Residual (leftover) heat from the formation of the Earth

Heat generated fromradioactive decay fromthe core of the earth

Hot Spots: Places on the Earth’s surface where plumes of __________ are rising up from the mantle not located along ________ _________ ________

magma

active Plate boundaries

As a plate passes over a hot spot, a _______________ _______________forms

CHAIN OF VOLCANIC MOUNTAINS

The tectonic plate moves over a fixed hotspot forming a chain of volcanoes.

The volcanoes get younger from one end to the other.

The only mountain that _______ ________ is the mountain located directly over the _____ ______

remainsactive

hot spot