Earth’s Structure Earth’s interior is made mostly of rock 4 main layers: 1) Inner Core 2) outer core 3) mantle 4) crust

Inner core Solid- made of iron and nickel Pressure from the other layers make it solid Compared to the seed of a peach

Outer Core Liquid Made mostly of iron and nickel Compared to the pit that covers the seed of a peach

Mantle Largest layer Contains silicon, oxygen, magnesium, and iron Upper mantle is plastic-like Compared to the juicy part of a peach

Crust Thinnest layer 2 types of crust- oceanic and continental Oceanic crust is thin and dense Oceanic crust is basaltic Until the 1960’s, we only had earthquake data that told us what oceanic crust was like Glomar Challenger- drilled for rock samples on the ocean floor

Science & New Ideas Without evidence, new ideas are not accepted 2 theories not accepted at first 1) Wegener’s ideas about continental drift 2) Alvarez and dinosaur extinction

Alfred Wegener Edges of some continents look like they would fit together like a puzzle

Alfred Wegener Wegener thought that all the continents were once connected in a landmass known as Pangaea (“all land”)

Alfred Wegener Wegener had no evidence, so his ideas were not accepted at first Wegener believed the landmass broke apart 200 million years ago Continental drift is the idea proposed by Wegener that the continents have drifted horizontally to their current locations,

Walter & Luis Alvarez Dinosaur extinction theory Believed that a large rocky object hit Earth, throwing tons of dust into the atmosphere, blocking out sunlight, leading to the death of the dinosaurs Meteorite impact or asteroid collision theory

Continental Drift Evidence for continental drift

Early Evidence Fossil and Climate Clues Rock Clues Seafloor Spreading

Fossil & Climate Clues MESOSAURUS Reptile that lived in freshwater Found in South America & Africa Continents must have been connected at one time because Mesosaurus could not have survived in ocean water

Fossil & Climate Evidence GLOSSOPTERIS Fern fossil Found in South America, Australia, India, & Antarctica Plants of warm climates can’t survive in cold climates, so at one time all places must have had similar climates

Rock Clues Similar rock structures are found on separate continents Appalachian Mountains and mountains of Europe line up Mountains of South America and western Africa line up If the continents had been together, then the mountain would line up and they do

Seafloor Spreading Echo sounding devices used to map the seafloor (SONAR) The ocean floor has mountains and valleys just like continents Mid-ocean rides form underwater mountain ranges

Seafloor Spreading Harry Hess proposed the idea of seafloor spreading Seafloor spreading is the idea that hot, less dense material in the mantle (magma) is forced up to the surface at mid-ocean ridges

Seafloor Spreading

Steps of seafloor spreading Magma is forced upward. It turns and flows sideways Carries seafloor away from mid-ocean ridge in both directions As the seafloor moves away, new magma comes out and forms new seafloor Seafloor cools and becomes more dense than the asthenosphere Cool seafloor then sinks down forming a trench

Age Evidence Glomar Challenger drilled for ocean floor samples The youngest rocks are at mid-ocean ridges and get older as you go away from the mid-ocean ridge

Age Evidence No rocks on the ocean floor were older than 160 million years old Continental rocks are approximately 4 billion years old

Magnetic Clues Earth’s magnetic field has reversed itself in the past Oceanic rock is basaltic, so it contains iron Iron aligns itself with the magnetic pole Rocks on the ocean floor show magnetic reversals

Plate Tectonics

Theory of Plate Tectonics Plate Tectonics Plate Boundaries Causes of Plate Tectonics

What is Plate Tectonics The Earth’s crust and upper mantle are broken into sections called plates Plates move around on top of the mantle like rafts

Plate Tectonics (1968) Theory of plate tectonics is a combination of the ideas of continental drift and seafloor spreading Theory of plate tectonics states the earth’s crust and upper mantle are broken into sections called plates; these plates move around on the mantle

Plate Tectonics Lithosphere is the crust and upper mantle (PLATES) Asthenosphere is the plastic-like layer below lithosphere The plates of the lithosphere are less dense than the asthenosphere

What is the Lithosphere? The crust and part of the upper mantle = lithosphere –100 km thick –Less dense than the material below it so it “floats”

What is the Asthenoshere? The plastic layer below the lithosphere = asthenosphere The plates of the lithosphere float on the asthenosphere

3 Ways plates interact 1.Move toward each other and collide (CONVERGENT) 2. Pull apart (DIVERGENT) 3.Move past one another (TRANSFORM FAULT)

Plate Movement Result of plate movement is seen at plate boundaries Movement along any boundary requires adjustment at another boundary For example, when the Pacific Plate and the North America Plate slide past one another, there are earthquakes in California and where the plate collides with another plate volcanoes form in Alaska

Tectonic Activities 1. Mountain building 2. Earthquakes 3. Volcanoes

2 Types of Plates Ocean plates - plates below the oceans Continental plates - plates below the continents

Plate Boundaries

Divergent Boundaries Boundary between two plates that are moving apart or rifting   RIFTING causes SEAFLOOR SPREADING Examples: Great Rift Valley & Mid- Atlantic Ridge

Features of Divergent Boundaries Mid-ocean ridges rift valleys fissure volcanoes

Convergent Boundaries Boundaries between two plates that are colliding   When crust is added in one place, it disappears in another.

Convergent boundaries 3 Types of Convergent boundaries 1.Oceanic crust collides with continental crust 2.Oceanic crust collides with oceanic crust 3.Continental crust collides with continental crust

Convergent Boundaries Ocean plate colliding with a less dense continental plate Continental plate is less dense than oceanic plate Oceanic plate sinks into mantle underneath continental plate because it is more dense

Convergent Boundaries Subduction zone forms where dense oceanic plate goes down into upper mantle Volcanoes form in subduction zones

Andes Mountains, South America

Convergent Boundary Ocean plate colliding with another ocean plate One ocean plate bends and goes under the other Volcanic island arcs are created above the subduction zone.

Aleutian Islands, Alaska

Convergent Boundary A continental plate colliding with another continental plate Continental plates are less dense than the mantle so the plates will not sink and form a subduction zone NO SUBDUCTION Mountain building takes place Example: Himalayas

Transform Fault Boundaries Boundary between two plates that are sliding past each other EARTHQUAKES occur along these faults Plates can move in opposite directions or same at different rate San Andreas Fault is an example

San Andreas Fault, CA

Causes of Plate Tectonics

Convection Currents Hot magma in the Earth moves toward the surface, cools, then sinks again. Creates convection currents beneath the plates that cause the plates to move.

Earthquakes Earthquake activity happens at all plate boundaries