Unit 3: The Dynamic Earth Mr. Ross Brown Brooklyn School for Law and Technology

How do the continents move about the surface of the earth? 5 October 2016 This question may require the use of the Earth Science Reference Tables. Base your answer to this question on the map below. The map shows the locations of deep-sea core drilling sites numbered 1 through 4. The approximate location of the East Pacific Ridge is shown by a dashed line. Point A is located on the East Pacific Ridge. At point A, the East Pacific Ridge is the boundary between the Cocos Plate and the North American Plate South American Plate and the Nazca Plate Pacific Plate and the South American Plate Pacific Plate and the Nazca Plate

Color Coding Word Wall Words Geology: Brown Astronomy: Red Meteorology: Green Oceanography: Blue

How do the continents move about the surface of the earth? 6 October 2016 This question may require the use of the Earth Science Reference Tables. Base your answer to this question on the map below. The map shows the locations of deep-sea core drilling sites numbered 1 through 4. The approximate location of the East Pacific Ridge is shown by a dashed line. Point A is located on the East Pacific Ridge. Compared to the thickness and density of the continental crust of South America, the oceanic crust of the Pacific floor is: thinner and less dense thinner and more dense thicker and less dense thicker and more dense will

Unit highlights Continental drift and how there was once a single landmass Seafloor spread as evidence of drift Plate tectonics Geologic activity at plate boundaries Lithospheric plates and convection

Coastlines lead to a hypothesis

What is Continental Drift? Mapmakers and explorers noticed similar shorelines on either side of the Atlantic Ocean Could the continents have once fit together? 1912- Alfred Wegener proposed the theory of Continental Drift; the continents had moved! This suggested a single landmass: Pangea Surrounded by super ocean Panthalassa

What is Pangea? From late Paleozoic to early Mesozoic eras Assembled from earlier continental units around 300MYA and began to break apart around 175MYA

Fossil evidence for Pangea and drift Similar fossils found on different continents Mesosaurus, alive 270MYA, found on Africa’s east coast and S. America’s west

Who was Mesosaurus?

What other evidence supports the theory of Pangea? Geological evidence Mountain ranges spanning continents Climatic evidence Glacial debris found across S Hemisphere landmasses that are today warmer

Was the theory of Pangea fully accepted? What was the force that made the continents drift apart?

What if continents hadn’t drifted?

Homework #2 6 October 2016 What observations first led to Wegener’s hypothesis of continental drift? What types of evidence supported Wegener’s hypothesis?

How do the continents move about the surface of the earth? 7 October 2016 This question may require the use of the Earth Science Reference Tables. Base your answer to this question on the map below. The map shows the locations of deep-sea core drilling sites numbered 1 through 4. The approximate location of the East Pacific Ridge is shown by a dashed line. Point A is located on the East Pacific Ridge. At which drilling site would the oldest igneous bedrock most likely be found? 1 2 3 4

Before we forget….. SITN Article #2 due on Tuesday Yes, Tuesday is a school day

What is the Mid-Atlantic Ridge? Undersea mountain range, with a steep valley running down its center. Part of an 80,000km system of mid-ocean ridges In 1940s scientists found that none of the rock there was older than from 175MYA Continental rock is from up to 4BYA!

What are Mid-Ocean Ridges

What is seafloor spreading?

How did the theory of seafloor spreading develop? What if the valley at the center of the ridge was a rift, or break? Magma wells up through this break Possible if ocean floor moves away from ridge If seafloor moved, then perhaps continents moved, too?!

How did our understanding of plate movements develop? 30 October 2015 Do now: How is ‘plate tectonics’ different from ‘continental drift?’

Plate tectonics The theory that Earth's outer shell is divided into several plates that glide over a plastic inner layer above the core. The plates act like a hard and rigid shell compared to Earth's interior.

11 October 2016 Do now: The map shows the continents of Africa and South America, the ocean between them, and the ocean ridge and transform faults. Locations A and D are on the continents. Locations B and C are on the ocean floor. Which graph best shows the relative age of the ocean-floor bedrock from location B to location C?

11 October 2016 Do now: The map shows the continents of Africa and South America, the ocean between them, and the ocean ridge and transform faults. Locations A and D are on the continents. Locations B and C are on the ocean floor. Which table best shows the relative densities of the crustal bedrock at locations A, B, C, and D?

11 October 2016 Do now: The map shows the continents of Africa and South America, the ocean between them, and the ocean ridge and transform faults. Locations A and D are on the continents. Locations B and C are on the ocean floor. The hottest crustal temperature measurements would most likely be found at location A B C D

How did seafloor spread refine the theory of plate tectonics? Moved beyond notion of “continental drift” Plate tectonics: the study of the formation of the earth’s crust Lithosphere: the rocky stuff. Crust and rigid mantle Asthenosphere: plastic rock on which lithosphere floats

Earth’s plates

What happens where tectonic plates meet? 13 October 2016 Do now: The diagram below shows a portion of Earth's interior. Point A is a location on the interface between layers. The arrows shown in the asthenosphere represent the inferred slow circulation of the plastic mantle by a process called conduction radiation insolation convection

What happens where tectonic plates meet? 14 October 2016 Do now: The map below shows the location of the Peru-Chile Trench. In which diagram do the arrows best represent the motions of Earth's crust at the Peru-Chile Trench?

What happens where tectonic plates meet? 14 October 2016 Do now: The map below shows the location of the Peru-Chile Trench. The Peru-Chile Trench marks the boundary between the Caribbean Plate and the Scotia Plate Nazca Plate and the South American Plate North American Plate and the Cocos Plate Pacific Plate and the Antarctic Plate

What happens where tectonic plates meet? Divergent Boundaries: plates move away from each other, forming rifts or mid-ocean ridges Mid-Atlantic Ridge Convergent Boundaries: plates collide Subduction: Oceanic pushed under continental Alaska’s Aleutian Islands Obduction: Continental pushed under oceanic Orogenic: both push upwards

Mid-Atlantic Ridge in Iceland

Aleutian Islands

What happens where tectonic plates meet? Transform Boundaries: Plates grind past each other California’s San Andreas Fault

What happens where tectonic plates meet?

What happens where tectonic plates meet?

How did the continents form? 2 November 2015 Do now: Why are there seashells on the tops of mountains?

How does subduction increase continental crust? As oceanic crust is subducted, some lithosphere is “scraped off” and accumulates on the continent. This is a terrane.

What is a terrane? Pieces of lithosphere with unique geological history

How is each terrane unique? A terrane contains rocks and fossils that are unique from its neighbors There are major faults at the boundaries of the terrane The magnetic properties of the terrane do not match its neighbors

What force makes the continents drift? 27 October 2015 Do now: Based on what we discussed yesterday, what is the force that moved the continents apart from Pangea, and still moves them today?