Plate Tectonics PPT Notes handout

pdf

School

University of the Fraser Valley *

*We aren’t endorsed by this school

Course

6222920930

Subject

Geography

Date

Oct 30, 2023

Type

pdf

Pages

Uploaded by CaptainJellyfishPerson759

© Science Is Real PLATE TECTONICS POWERPOINT NOTES Name: A. Continental Drift 1. In 1915, Alfred Wegener proposed his radical theory of continental drift: • All together to form a supercontinent • He named the supercontinent , meaning all land • Pangaea began breaking up into smaller continents and drifted apart about million years ago 2. Alfred Wegener presented a variety of evidence to support his hypothesis of He could see on different continents separated by a vast ocean that: • Coastlines matched up like • Similar plant and animal existed • They had matching and mountain chains • Glacial evidence showed they shared a • His Hypothesis Was Rejected! He had evidence that continents drifted apart, but he could not say HOW the continents drifted. B. Marie Tharp and Harry Hess – Exploring the Ocean Floor 3. Although Alfred Wegener correctly defined continental drift, he continents drifted apart. • Eventually, other scientists took interest in his hypothesis when new data came from one of the least-known parts of the Earth – the ocean floor 4. Marie (1920-2006) created the first scientific map of the entire ocean floor. Harry (1906-1969) found evidence of sea-floor spreading 5. In the early 1900s, Sonar was used to calculate the distance to the ocean floor from an ocean vessel. • In 1960, Harry Hess used SONAR images to explain the mechanism behind continental drift • Sea-Floor Spreading: • • This helped establish respec t of Wegener’s earlier hypothesis of continental drift within the scientific community. C. Deep Ocean Trenches 6. As scientists mapped the ocean floor, they found deep-ocean • Long, along the edges of some ocean basins • The deepest trench on Earth is the • Within the Mariana Trench lies the : o The deepest place on Earth o Almost 11,000 meters or 36,000 feet deep! • As new ocean floor emerges, the Earth does not get any larger. • To accommodate the newly created lithosphere, • Subduction occurs when the ocean sinks into the mantle beneath a • A location where subduction occurs is called a D. Mid-Ocean Ridges and Sea-Floor Spreading 7. Mid-ocean ridges are long chains of extending the length of the ocean. • Longest feature on Earth’s surface • Spans 70,000 km through all major ocean basins • 1,000 to 4,000 kilometers wide (620-2500 mi)

© Science Is Real 8. Mid-ocean ridges form as a result of submarine volcanic activity • Fractures along the central valley of a mid-ocean ridge fill with • Magma cools and in a process called sea-floor spreading 9. Harry Hess, published his hypothesis of sea-floor spreading in 1963 • In the process of sea-floor spreading, • The floor then slowly across ocean basins • Finally, the sea-floor sinks back into the mantle deep ocean trenches 10. During sea-floor spreading and the ocean floor gets wider. • Evidence of sea-floor spreading include: • : Alternating magnetic stripes in ocean-floor rock • : Shallow earthquakes form near a trench; Deep earthquakes form in a belt farther away from a trench • : Younger rock near the mid-ocean ridge and older rock farther away from the ridge 11. Alternating Magnetic Stripes: • Stripes of rocks that formed when Earth’s magnetic field pointed north with stripes of rock that formed when the magnetic field pointed south. 12. Movement of Ocean Floor • As , older ocean floor moves outward and away from the ridge on both sides. E. Rift Valley 13. Rift valleys are found on land and in the ocean. Created by the process of sea-floor spreading • Often a rift valley • Central valley of a mid-ocean ridge that resembles a • Rift valleys can form on land when volcanic activity splits a continental landmass. • Eventually the rift valley will widen enough to form a new ocean basin • The is splitting apart Asia and Africa F. Tectonic Plates and Earth’s Crust 14. The is broken into several large pieces called 15. There are two types of crust that make up tectonic plates • Oceanic Crust: than continental crust and made up mostly with rock • Continental Crust: than oceanic crust and made up of rock with rock • Because is less dense, it higher on the mantle • Since crust is denser, it under the continental crust. G. Plate Motion and Convection Currents 16. In the mantle, churn the molten rock material, moving the tectonic plates.

© Science Is Real • A convection current is the that occurs in a fluid because of differences in • Cool material is denser and • Warm material is less dense and 17. In the 1960s, a theory of plate tectonics emerged: • Earth’s lithospheric • Hot material deep in the mantle moves upward by convection • Cooler, denser slabs of lithosphere sink into the mantle 18. Plates movement averages about • About as fast as a fingernail grows • This results in H. Plate Boundaries 19. Where two plates meet is called a • There are three types of plate boundaries: Divergent, Convergent, and Transform Fault Boundaries 20. Divergent Plate Boundaries: • Plates and are spreading centers located mostly along the crests of mid-ocean ridges. • Some occur on continents and create rift valleys • boundary – New crust is created 21. Convergent Plate Boundaries: • Plates and interact producing • boundary: lithosphere is destroyed • When a , the less dense continental plate will remain floating and the ocean plate will subduct. • Newly formed magma may reach the surface and form a : a range of volcanic mountains produced in part by the subduction of oceanic lithosphere • When , one subducts under the other. • Volcanoes will form on the ocean floor and eventually build a chain of volcanic structures that form a chain of islands called a • The • Because continental lithosphere is less dense than oceanic crust, it is not subducted. 22. Transform Plate Boundaries: • This boundary is not destructive or constructive • Plates • Most transform boundaries join two segments of a mid-ocean ridge • The in California is a transform fault that occurs on land • are more common near plate boundaries than any other type I. Volcanism and Plate Boundaries 23. Most volcanoes form along divergent and convergent boundaries. • The is a long belt of volcanoes that circles the Pacific Ocean 24. Some volcanoes form at , locations away from plate boundaries • is volcanic activity that occurs within a plate, not at the boundary between plates.

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help

© Science Is Real J. Comprehension Checks 1. How did the discoveries of Harry Hess and Marie Tharp support Wegener’s hypothesis of continental drift? 2. List three pieces of evidence for sea-floor spreading. 3. Compare the physical and chemical properties of oceanic and continental crust. 4. List three landforms that can occur as a result of convergent boundaries. 5. What is the name of the belt of volcanoes that circle much of the Pacific Ocean? 6. Draw a model of the following convergent boundaries: • Oceanic-Oceanic • Oceanic-Continental • Continental-Continental 7. Draw a model of a transform boundary. 8. Draw a model of sea-floor spreading at a mid-ocean ridge.