CH 9 PLATE TECTONICS

Roots:Derm = skin (dermatitis)Diplo = two (diploid)Dis – away (disappear)Dia = through (diagonal)Dict = speak (dictate)Domin = master (dominate)Don = give (donation)Duct = lead (conduct)Du = two (duplicate)Dur = lasting (durable)

Past or Future?

Future Plates: http://earth.rice.edu/MTPE/geo/geosphere/topics/plate_tectonics/plate_future.mov

“Alfred! ALFRED! ALFRED WEGENER!”

Do you think when Alfred’s mom called him in for dinner she had even the slightest idea what a monumental effect her son would have on the world as we understand it?

Alfred grew up to develop the hypothesis of CONTINENTAL DRIFT.

He proposed that there had been a supercontinent in Earth’s past and he named it PANGAEA.

ACTIVITY: Making Pangaea puzzles.

Evidence for Continental Drift: The Continental Puzzle!

Evidence:The continents fit together like a mega-puzzle.

Bullard Fit of Continents: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Evidence for Continental Drift: Fossils!

Breaking up is so hard to do!

“It’s not you

… it’s me.“

“Let’s just be friends.”“We need to talk…”

“You’re like a brother to me.”

“Give me my ring.”Pangaea breakup (slow-mo)http://www.agci.org/classroom/geosphere/index.php

Continental Drift as Linked to Paleologic Time Scalehttp://www.wiley.com/college/strahler/0471480533/animations/ch13_animations/animation3.html

Grenville Orogeny

Evidence for Continental Drift: Continuous Mountains!

Mountain Ranges:

Ranges of mountains that stretch across multiple continents that once were attached.

These mountains have the same rocks and composition.

Evidence for Continental Drift: Continuous Climates!

Wegener is rejected! ?Wegener couldn’t explain the mechanism (what was the force) that allowed the plates to move.

A few scientists continued to search for answers.

Magnetic Reversals: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Evidence for Continental Drift: Paleomagnetism!

1. Magnetic iron-rich rocks heat up.

2. Lose their magnetism.3. Cool down.4. Become re-magnetic in

a direction parallel to the existing magnetic field around earth.

Pg 266 Figure 17

Normal polarity = when rocks show the same magnetism as the current magnetic field.

Reverse polarity = when rocks show opposite magnetism to the current magnetic field.

Evidence for Continental Drift: Earthquake Patterns!

Relationship between deep focus earthquakes and ocean trenches.

Pg 267 Figure 181. Earthquakes are produced during subduction where rocks are

weak.2. Shallow-focus quakes are produced in the weak rock as the

descending plate sinks.3. As the descending plate (and weak rock section) goes deeper the

earthquake foci become deeper.4. No earthquakes have been produced below 700 km. This is where

the rock begins to soften and melt.

Weak Rock

Evidence for Continental Drift: Ocean Drilling!

The Deep Sea Drilling Project

1968-1983The Glomar

Challenger drilled into the ocean floor.

Youngest rocks are closest to the ridge.

Older

Young Oldest

Evidence for Continental Drift: Hot Spots!

Formation of Hawaiian Island Chain http://www.teachersdomain.org/resource/ess05.sci.ess.earthsys.hawaii/rm

By 1968, a new theory was developed – Plate Tectonics.

The formation of hot spot islands in a chain that corresponds with the movement of the plate.

Hawaii

Animated Plate Boundaries (shows divergent, convergent, and transform)http://www.seed.slb.com/subcontent.aspx?id=5046

Divergent = separating

Convergent = coming together

Transform = sliding past each other

HSW: Earth Science: The Spreading Seafloor Time: 04:01

Seafloor Spreading = the process by which plate tectonics produces new oceanic lithosphere.

Pg 259 Figure 9

• Upwarping occurs• Rift valley is created• Linear sea developes• Oceanic ridge builds• Continents drift apart

- Averages 5 cm/yr- All of Earth’s oceans could have been created within the last

200 million years. (Oldest found is 180 my)

Sea Floor Spreading & Formation of Oceanic Crust: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Iceland

Iberia iceland

Divergent Boundaries = where plates move away from each other

Basic Plate Boundaries: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Continental Rifts = areas where spreading develops within a continent.

East African Rift Valley

The Process of Rifting: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Convergent Boundaries = where plates come together

Basic Plate Boundaries & the Process of Subduction: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Ocean – Continent Subduction Zone:Where an ocean plate is forced below a continental plate.

Continental Volcanic Arc = where volcanic mountains are created due to subduction.

Andes

Ocean – Ocean:Where two ocean plates collide.

Convergent Boundaries:

Aleutian IslandsIsland Arc Formation: http://esminfo.prenhall.com/science/geoanimations/animations/35_VolcanicAct.html

Continent – ContinentWhere two continental plates collide.

Continental plates are buoyant so neither wants to subduct below the other. As a result they simply collide and push up mountains.

Formation of Himalayas:http://www.classzone.com/books/earth_science/terc/content/visualizations/es1105/es1105page01.cfm?chapter_no=visualization

Himalayas

Transform Boundaries = where plates slide past each other

Basic Plate Boundaries & Transform Faults: http://www.wwnorton.com/college/geo/egeo/animations/ch2.htm

Why do the Tectonic Plates Move?

Main Reason: Convection. Convection in a pot of water.

Convection around a heater.

Convection at the sea shore.

Why do the Tectonic Plates Move?

Slab-Pull = downward movement of convectional flow.

Ridge-Push = sliding down of sides of ridge and pushing outward from the ridge.

Flash: Continents Adrift