Part I of Plate Tectonics

The origins of plate tectonics The idea that the Earth’s surface might be moving is not new. As early as the 17th century scientists noticed the puzzle fit of many land masses on Earth.

In 1912 a German scientist named Alfred Wegener proposed the Continental Drift Hypothesis as a means of explaining this phenomenon.

What is continental drift? Hypothesis that proposed that the continents have moved from one location to another over time. At one time, there was a single, supercontinent, called Pangaea.

Pangaea 225 MYA (Permian Period)

Continental Drift in Action: The Break-up of Pangea 25 MY ▪ Formation of Gondwanaland and Laurasia

Continental Drift in Action: The Break-up of Pangea 135 mya 70 MY Breakup of Pangea

Continental Drift in Action: The Break-up of Pangea 65 MY Present Day! Death of Dinosaurs

What evidence did Wegener use to support his hypothesis of continental drift? Puzzle fit of Africa & South America 2. Fossil evidence 3. Distinctive mountain and rock formations All Wegener’s support was based on observations!! 4. Climate change evidence

Puzzle fit of Africa & South America

2. Fossil Evidence

2. Fossil remains of Mesosaurus

3. Distinctive rock Formations Age of rocks are the same on several continents.

3. Mountain Ranges Correlate Mountain ranges terminate at same position across the world.

4. Paleoclimate change evidence Glacial Deposits at Equator Coral Reefs in Antartica

Based on this evidence, do you think that Wegener’s peers supported his continental drift theory? The theory was rejected because it could not explain HOW the continents had moved. NO

The origins of plate tectonics In the 1950’s & 1960’s, discoveries led other scientists to re-examine Wegener’s continental drift theory. These scientists found that while the continents did not move the way Wegener suggested, something was moving . . . . . .

What is the Plate Tectonic Theory? They proposed the theory of plate tectonics! What is the Plate Tectonic Theory? The theory that the lithosphere is made of plates that move on the asthenosphere and interact with one another.

Egg analogy!

Add the following notes to your foldable

The Crust Thinnest Layer-Average 30 km Composed of Oxygen and Silcon based rocks Solid oceanic crust Very dense continental crust lighter

Largest layer of the Earth –average 2900 km Composed of silicate rocks rich in magnesium and iron. Molten rock with convection currents constantly moving. Upper mantle and lower crust make the ASTHENOSPHERE.

Convection Currents The middle mantle "flows" because of convection currents. Convection currents very hot material at the deepest part of the mantle rising, then cooling and sinking again repeating this cycle over and over.

The Outer Core Average 2300 km thick composed of the melted metals of nickel and iron. very hot liquid

The Inner Core 1,216 km Thick Made of nickel and iron high temperatures and pressures Solid!

Evidence that supports plate tectonics Seafloor spreading 2. Earth’s Paleomagnetic Record 3. Location of Earthquakes & Volcanic Hotspots

1. Sea Floor Spreading The process by which new ocean floor is formed by lava erupting from a crack, pushing the existing floor outward. Youngest rock is near the center. Atlantic Ocean is getting larger.

2. Earth’s Magnet Field Metals in Earth’s liquid outer core are always moving (convection currents) AND Earth is always moving. When metal moves electric currents are created this produced a magnetic field.

Paleomagnetic Record Lava and sediments contain iron-bearing minerals When they cool or are deposited on the iron lines up with the Earth’s magnetic field. If the Earth’s magnetic field switches then the iron lines up differently. This is known as 'paleomagnetism'.

Paleomagnetic Record

The magnitism moves out on each side like a mirror. The youngest oceanic crust is at the ridge crest, and the oldest oceanic crust is at the continental margins. The magnitism moves out on each side like a mirror. Youngest Oldest

Practice Question!

3. Locations of Earthquakes and Volcanoes Earthquakes and volcanoes do not occur randomly throughout the world. They occur primarily in concentrated belts, near plate margins!

3. Locations of Earthquakes and Volcanoes

The crust! Crust is divided into two groups. Oceanic- underwater, dense crust Continental- land, lighter Plate boundaries are where lithospheric plates meet. What happens at the boundary depends on the type of crust and the direction of the movement.

Plate Boundary Notes Add to your table of contents: Plate Boundary Notes / 2.1.1 Turn to that page and divide the paper into thirds. Use chapter 17.3 to label each section with the three types of plate boundaries. Draw a picture of each (convergent should have at least two drawings). Make sure they are labeled. Leave space to write notes tomorrow.

The major plates of Earth

Divergent (apart) Boundary Continental-Continental Rift Valley

Divergent boundary of two continental plates. Creates a rift valley. Example: East African Rift

Divergent (apart) Boundary Continental-Continental Rift Valley Oceanic-Oceanic Mid-Ocean Ridge

Oceanic - Oceanic Divergent boundary creates a mid-ocean ridge creates new land

Iceland Mid-Atlantic Ridge

Convergent (together) Boundary Oceanic-Continental Volcanic mountain range and trench Slab-Pull model

Convergent boundary of an oceanic plate and a continental plate Convergent boundary of an oceanic plate and a continental plate. Forms a volcanic mountain range and a trench. Examples: Cascades or Andes Mts

Convergent (together) Boundary Oceanic-Continental Volcanic mountain range and trench Slab-Pull model Oceanic-Oceanic Trench and Island Arcs

Convergent boundary of two oceanic plates Convergent boundary of two oceanic plates. Creates an island arc and a trench. Example: Japan

Slab- Pull .

Convergent (together) Boundary Oceanic-Continental Volcanic Mountain Range and Trench Slab-Pull Model Oceanic-Oceanic Trench and Island Arcs Continental-Continental Mountain Range

Convergent boundary of two continental plates Convergent boundary of two continental plates. Forms a folded mountain range. Examples: Himalayas, Alps, Appalachian

Transform (sliding) Boundary Two plates sliding past each other. Forms a fault Strike-Slip

Example: San Andreas Fault in California

How fast does all of this happen?????? SLOWLY Approximately 5 centimeters per year

Practice Questions Places where plates move apart are called _____________ boundaries. When continental plates diverge a ___________ is formed. When two oceanic plates converge what is created? _________________ The Appalachians formed mainly from continental plate collisions and therefore are a __________ mountain range. The force moving the plates is ____________ .

Tectonic Plate Mapping / 2.1.1 Answer the Pre-Lab questions #1-5 and 13, 14 on the back of your map or in your notebook on a new page. Use a textbook if needed. (15 minutes) Label the map AS A CLASS to set up for our activity tomorrow. Make sure your name is on your map and turn it in.

Hot Spots / 2.1.1 Turn to page 486 in the textbook. Read the section on Hot Spots. Answer the following: What is a hot spot? What US state was formed by a hot spot? Based on the age of the oldest island in the Hawaiian island chain, approximately how old is the hot spot that formed Hawaii?

Hot Spots / 2.1.1 Hot spots are areas of volcanic activity in the middle of lithospheric plates. Lava at hot spots usually flows smoothly over the surface. Hot spots remain in the same location even though the lithospheric plate above it moves. The most famous example of hot spot volcanism is ____________________.

Hot Spot Activity Complete the activity as a class. Answer Questions #1-6 on the same page in your notebook.

Test Remediation Test Corrections Boundaries diagram Seafloor diagram #, Letter, Explanation Explanation cannot be rewriting the questions. Must be definitions, diagrams, examples or descriptions Boundaries diagram Seafloor diagram