Plate Tectonics Chapter 10 POD 2508 1 Summarize

Plate Tectonics Chapter 10

POD 2/5/08 1. Summarize theory of plate tectonics. Using arrows to draw/label the three types of plate boundaries. Give an example of each.

Problem of the Day (POD) 1/30/08 1. Who proposed theory of continental drift. What mechanisms led to this theory being accepted in the science community?

POD 2/1/08 1. How are tectonic plate boundaries related to earthquakes? What are three types of plate boundaries?

Section 1 Objectives Summarize Wegener's hypothesis of continental drift. Describe the process of sea-floor spreading. Identify how paleomagnetism provides support for the idea of sea-floor spreading. Explain how sea-floor spreading provides a mechanism for continental drift.

Wegner’s Hypothesis Ø 1912 German Scientist Ø Proposed Continental Drift Ø Supercontinent- began breaking into smaller continents 250 million years ago Ø Over millions of years continents drifted to present locations

Evidence to Support Fossil Evidence Ø Fossils of same plant and animals found in areas that had once been connected Rock Formations Ø Ages and types of rocks in coastal regions matched closely Western Africa and Eastern South America

Evidence to Support Climatic Evidence Ø Geologists discovered layers of debris from ancient glaciers in Southern Africa and South America Ø Areas today are to warm for glaciers Missing Mechanisms Ø Idea strongly opposed and rejected Ø Continents plowed through ocean floor Ø Easily disproved by geologic evidence

Mid-Ocean Ridges 1947 scientists set out to map Mid-Atlantic Ridge Findings Ø Rocks closer to the ridge Ø are younger than rocks farther from the ridge Ø Ocean floor is very young 175 million years Ø Rocks on land 3. 8 billion

Sea-Floor Spreading H. H. Hess- proposed sea-floor spreading Ø Center of a ridge has a crack or rift in Earth’s crust Sea Floor Formation 1. Earth rises to fill crack 2. As ocean floor moves outward 3. Magma cools and solidifies Hypothesis- Wegener's missing mechanism If the ocean floor was moving, so were the continents?

Paleomagnetism Earth’s magnetic field not always pointed north Magnetic Reversals magnetic field north= normal polarity Magnetic field south= reversed polarity Pattern alternating normal/reversed Geomagnetic Reversal Time Scale Magnetic Symmetry Match magnetic patterns on each side of mid-ocean ridge- rock ages could be assigned

Wegener Redeemed ü Magnetic patterns show changes over time ü Sea-floor spreading provided a way for continents to move over Earth’s surface ü Became accepted in scientific community Mechanism that verified Wegener’s hypothesis

Section 2 Objectives Summarize theory of plate tectonics. Identify and describe three types of plate boundaries. List and describe three causes of plate movement.

How Continents Move Continents and Oceans are carried along moving tectonic plates Lithosphere Ø Upper part of mantle Ø Broken into tectonic plates which ride asthenosphere Asthenosphere Ø Plastic rock Earth’s Crust Ø Oceanic and Continental

Tectonic Plates Scientist Identify Ø 15 major tectonic plates Ø By way of Earthquakes and Volcanoes Three Types of Plate Boundaries 1. Divergent 2. Convergent 3. Transform

Divergent Boundaries Two plates move away from each other Ø Commonly found on ocean floor Ø Magma rises as plates move apart forming new lithosphere Mid-ocean ridges

Convergent Boundaries Two plates collide with one another 1. Continental-Oceanic= subduction 2. Continental-Continental= uplift 3. Oceanic-Oceanic= deep-ocean trench/island arc

Transform Boundaries Two plates slide past one another Scrape and cause stress= earthquake No magma is produced San Andreas fault

Causes of Plate Motion Mantle Convection Hot material rises- cooler denser material flows away

Causes of Plate Motion Ridge Push Cooling rock sinks forcing plate away from mid-ocean ridge

Causes of Plate Motion Slab Pull Plates pull away from each other at midocean ridges

Section 3 Objectives Identify how movements of tectonic plates change Earth’s surface. Summarize how movements of tectonic plates have influenced climates and life on Earth. Describe the supercontinent cycle.

Pyramid 1. Place sheet of paper in front of you. Fold lower left corner of the paper diagonally to the opposite edge of the paper. 2. Cut off the tab of paper created by the fold. 3. Open paper so that it is a square. Fold lower right corner of the paper diagonally to the opposite corner to form a triangle. 4. Open the paper. The creases of the two folds will have created an X. 5. Using, scissors, cut along one of the creases. Start fron any corner, and stop at the center point to create two flaps. Attach one of the flaps on the other.

Reshaping The Earth’s Crust Side 1 Ø Define rifting Ø How does the Earth’s crust break/crack? Ø Define terrane. Ø List 3 characteristics of terranes Ø Where do terranes become part of the continent?

Effects of Continental Change Side 2 Ø What effects a continents climate? Ø What Geologic evidence supports changes in climate? Ø How are species/populations affected from continetal rifting or the formations of mountains?

Supercontinent Cycle Side 3 Ø Why supercontinents form? Ø Formation of Pangaea- time/mountain ranges Ø Breakup of Pangaea Ø The Modern Continents On the bottom of your pyramid list three changes in geography that are likely to happen in the future

Reshaping Earth’s Crust Rifting Process by which a continent breaks apart

Terranes and Continental Growth Terrane- unique geologic history Contains rock and fossils Major fault boundaries Properties do not match neighbors Small volcanic islands, sea-mounts, atolls

Effects of Continental Changes in Climate Ice covered most of Earth’s surface- even the Sahara Ice sheet formed when continents were close Global temperatures changed as continents drift Changes in Life

Effects of Continental Changes in Life As continents rift mountains form, organisms are separated New species evolve

The Supercontinent Cycle

Geography of the Future