Plate Tectonics Part A- Theory of Plate Tectonics

Name ______Date ______Per ______

Plate Tectonics Part A- Theory of Plate Tectonics Old 7th Grade Text Chap 14:3 Continental Drift Hypothesis • In 1912 ______suggested that all the continents were once connected as one large landmass now called ______• Pangaea means “______” • The land mass broke apart about ______years ago and • The ______slowly drifted to their present positions

Seafloor Spreading-explains the ______of the continents • Hot dense material below the Earth’s ______rises upward to the surface at the mid-ocean ridges • Then it flows sideways, carrying the ______way from the ridge. • As the new seafloor spreads apart, ______moves up and flows from the cracks, cools, and forms new seafloor. • ______rocks are located at the mid-ocean ridges and become increasingly older the further out you go.

Plate Tectonics • In the 1960’s scientists developed a new theory that ______continental drift and seafloor spreading. • It is called ______

Plate Tectonics • The Earth’s ______and upper mantle are broken into sections. • The sections, called ______, move on a plastic-like layer of the mantle – Geologists use the term ______to describe the consistency of rock that flows but is not a liquid like Silly Putty, modeling clay, or toothpaste.

Plate Tectonics • The plates and upper mantle form the ______. – The lithosphere is about ______thick and generally is less dense than the material underneath. • The plastic-like layer is called the ______– The rigid plates of the lithosphere float and move around on the asthenosphere • When plates move, they can interact in several ways. – They can collide into each other, or pull apart, or slide alongside each other • When plates interact, the result of their movement can be seen at the ______

Plates moving ______- Divergent Boundaries • Plates moving apart at the ______are examples of divergent plate boundaries – In the ______Ocean, the North American Plate is moving away from the Eurasian and the African plates. – The ______in eastern Africa may become a divergent boundary. The continental plate is being pulled ______. Plates moving ______- Convergent boundaries • As new crust is added in one place, it ______below the surface at another. Plates moving together- convergent boundaries • When Ocean and Land Plates meet: – The denser oceanic plates sink under less ______continental plates – The area where the ocean plate moves down is called a ______– This type of convergent boundary forms a ______Plates moving together- convergent boundaries • When Ocean and Land Plates meet (continued): – Newly formed hot ______is forced upward along the subduction zones and forms volcanic mountains – The ______Mountain Range in South America contains many volcanoes that were formed at the ______boundary of the Nazca and South American plates

Plates moving together- convergent boundaries • When Two Oceanic Plates Collide – The older, denser plate will ______and sink down into the mantle. – The ______in the Western Pacific are a chain of volcanic islands formed from two oceanic plates ______.

Plates moving together- convergent boundaries • When Two Continental (Land) Plates Collide – There is usually ______because both of these plates are less dense than the material of the ______. – Plates will crumple up to form ______ranges. – ______are common here, but not volcanoes. – The ______in Asia are forming where the Indo-Australian plate collides with the Eurasian Plate

Plates Sliding Past each other- ______Boundary • When one plate slips past another suddenly ______occur – The Pacific Plate is ______past the North American Plate forming the famous ______in California.

Causes of Plate Tectonics • ______inside the Earth – Cycle of heating, rising, cooling and sinking is called convection current. – This process occurring inside the ______of the earth is the driving force behind ______.

Features caused by Plate Tectonics • The interaction of plates produces forces that build ______, create ______, and cause ______. • When rocks in the Earth’s crust break and move the energy is released as ______waves • We feel this release as ______Features caused by Plate Tectonics • ______, Faults and ______Valleys – are formed at divergent boundaries where plates are pulled apart. • Mountains and ______– are formed at convergent boundaries where plates collide. • Strike-Slip faults- cause of ______are found at transform boundaries where plates grind past each other.

Testing for Plate Tectonics • Using lasers and satellites, scientists can measure ______as little as 1 cm per year. – ______is moving toward Japan at a rate of about 8.3 cm per year. – Maryland is moving away from ______at a rate of 1.7 cm per year • Scientists have observed that the plates move at rates from about ______to ______per year.

Section Assessment- use a separate sheet, answer the following questions. 1. What happens to plates at a transform boundary? 2. What occurs at plate boundaries that are associated with seafloor spreading? 3. Describe the three types of plate boundaries where volcanic eruptions can occur. 4. How are convection currents related to plate tectonics? 5. Using a flow map- describe the three theories that were discussed at the beginning of the section.