2The Theory of Plate Tectonics The theory that Earth’s lithosphere is divided into tectonic plates that drift on the athenosphere.Divided into seven to eight main plates and several smaller ones.The plates move by convection currents that either push the plates apart, together or make them slide against one another.
3Divergent Plate Boundaries Oceanic: Where two oceanic plates move apartMagma from the mantle flows up into the space between the plates and the magma hardens to form new oceanic crust.This process is called sea-floor spreading.Causes the oceans to widen!!Long, continuous chains of underwater volcanoes form along the boundaries and are called mid-ocean ridges.
4*What happens to the ocean during a divergent boundary? *What forms on each sides of the divergent boundary?*What new is being formed where the magma hardens?Note: The Mid-Atlantic Ridge is created by this and moves North America and Europe further apart.
5Divergent Plate Boundaries Continental: Where two continental plates move apartSince continental crust is MUCH thicker, it doesn’t split fully causing a big ridge.The ridge can allow rivers to form in it and as it continues to split can allow ocean waters to flow in as well.The Red Sea was formed when two continental plates diverged.
6What would fill in the rift valley above *What would fill in the rift valley above? *Why didn’t the plates split all the way? *The faulted valleys will cause what phenomenon?
7Convergent Plate Boundaries Oceanic = 2 plates made of oceanic crust collideOne plate is pushed under the otherSubduction zone – region where one plate slides under another plateA deep canyon (trench) forms under the ocean where the plates meetThe plate sinks into the hot mantle and melts to form magmaCreates a chain of undersea volcanoesAs they keep erupting and forming new land, they will rise above the ocean floor and form volcanic islandsThe Aleutian Islands formed this way.
8What happens to the plate that slides underneath? What is eventually formed after years of underground volcanic eruptions?
9Convergent Plate Boundaries Continental-Oceanic Boundaries = 1 oceanic plate collides with 1 continental plateThe oceanic plate slides under the continental plate due to the increased densityThis also forms a trench and volcanic mountains form next to the trench on the continental plateThe western coast of South America have many volcanoes formed this way.
10Which plate slides under the other? What is formed on the continental plate?
11Convergent Plate Boundaries Continental = 2 continental plates collideCreates the highest mountains in the world!Folded mountains – the rock layers are squeezed together causing folds in the crustThe plates buckle and thicken.Created: The Himalays, the Alps, The Ural Mountains and the Great Smoky Mountains
12What are these types of continental mountain ranges called? What makes these mountain ranges so special?
13Transform Boundaries Two plates slide against each other Cause the most earthquakes!When they slide, pressure builds up and some rock breaks or slips and releases energy in the form of seismic waves.Seismic wave – a wave of energy that travels away from the center of an earthquake in all directionsFault – The break or crack along Earth’s surface where movement occurs.
14Transform boundaries causes the most…? What is a fault?
15Hot SpotsHot Spot – an area of volcanic activity (usually in the middle of the plate)Stays in the same place even though the plate movesResults in a chain of volcanoes some of which are no longer activeCreated the Hawaiian IslandsDue to a hot spot in the Mantle
16Ring of FireRing of Fire – zone of frequent volcanic eruptions and earthquakes encircling the Pacific Ocean basin.Contains more than 75% of all volcanoes on EarthLocated along the boundary of the Pacific PlateMostly caused by subduction of plates resulting in melting magma.
19Question 11. True or False: Earthquakes can occur at any type of plate boundary.
20Question 1 AnswerTrue! Faults can occur anywhere there is a crack and pressure is built up releasing energy and causing seismic waves.
21Question 22. At which location are earthquakes mostq likely to occur? A. At a boundary where plates push together B. At a boundary where plates pull apart C. At a boundary where plates slide by each other D. In the middle of the plate
22Question 2 AnswerTransform plate boundaries (where two plates slide against one another) cause the most earthquakes because they cause the most faults.
23Question 3A chain of mountains is located near the western coast of a continent next to a plate boundary. Which sentences describes how the mountains most likely formed?A. As a continental plate and an oceanic plate slide past each other, a fault formed, and mountains were exposed by earthquake movement.B. As a continental plate and an oceanic plate collided, part of the oceanic plate subducted, and volcanoes erupted, forming the mountains.C. As two oceanic plates collided, one of the oceanic plates subducted, and the other plate rose to the surface, forming mountains.D. As two oceanic plates moved apart, new seafloor was produced, forming a ridge.
24Question 3 AnswerB! When a continental and oceanic plate collides, the oceanic plate subducts below the continental and volcanic mountains are created on the continental plate.
25Question 4What is the region where one plate slides under another plate called?A. An earthquake zoneB. A hot spotC. A volcanoD. A subduction zone
26Question 4 AnswerD. When one plate slides under another, it is called a subduction zone.
27Question 5Which landforms is most likely to form where two oceanic plates push together?A. Folded mountainB. Mid-ocean ridgeC. River valleyD. Volcanic island
28Question 5 AnswerD. One oceanic plate subducts under the other and melts. This produces magma and many undersea volcanoes. When these break the surface of the water, volcanic islands are formed.
29Question 6 Where does sea-floor spreading occur? A. Where two oceanic plates collideB. Where an oceanic plate and a continental plate collideC. Where two oceanic plates pull apartD. Where two continental plates pull apart
30Question 6 AnswerC. As two oceanic plates pull apart, magma is exposed creating new sea floor and the ocean expands.
31Question 7 A hot spot can produce: A. A chain of islands B. A mid-ocean ridgeC. A trenchD. A tectonic plate
32Question 7 AnswerA. A hot spot will produce a chain of islands. As a plate moves over a hot spot, it will form volcanoes, keep moving and then form another.