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Inside the Earth. Composition (What it is made of). Crust (where we live) Mantle (hot) Outer Core (even hotter) Inner Core (HOTTEST). Draw and label this diagram. The Four Layers.
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Composition (What it is made of) • Crust (where we live) • Mantle (hot) • Outer Core (even hotter) • Inner Core (HOTTEST)
The Four Layers The crust is the layer that you live on and most widely studied and understood. The mantle is much hotter and has the ABILITY TO FLOW. The outer core and inner core are even hotter with pressures so great you would be squeezed into a ball smaller than a marble if you were able to go to the center of the Earth!
Outer layer 2 types of crust Continental (less dense, made of granite) Oceanic (very dense, made of basalt) The Crust
The Crust Continental Plate The CRUST is composed of two rocks. The continental crust is mostly granite. The oceanic crust is basalt. Basalt is much denser than the granite. Because of this the less dense continents ride on the denser oceanic plates. Oceanic Plate
The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere. lithosphere
Middle layer Very thick layer The Mantle
The Mantle The Mantle is the largest layer of the Earth. The middle mantle is composed of very hot dense rock that flows like asphalt under a heavy weight. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move.
The Asthenosphere The asthenosphereis the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight.
The Outer and Inner Core • Made mostly of iron • 1/3 of the earth’s mass • Very hot
How are the earth’s layers similar to an egg? Shell=crust Egg white=mantle Yolk=core Earth’s Layers
Physical Structure of the Earth(5 Layers) • Lithosphere- rigid outer layer (crust) • Asthenosphere- solid rock that flows slowly (like hot asphalt) • Mesosphere- middle layer • Outer Core- liquid layer • Inner Core- solid, very dense
Convection Currents The middle mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over.
Convection Currents The next time you heat anything like soup or water in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the asthenosphere they also move the crust. The crust gets a free ride with these currents, like the cork in this illustration. Safety Caution: Don’t get your face too close to the boiling water!
The Outer Core The core of the Earth is like a ball of very hot metals. The outer core is so hot that the metals in it are all in the liquid state. The outer core is composed of the melted metals of nickel and iron.
The Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid.
Plate Tetonics Defined • Plate tectonics is the theory that the outer rigid layer of the earth (the lithosphere) is divided into about a dozen " plates" that move across the earth's surface relative to each other, like slabs of ice on a lake
Continents • Click and drag • http://www.playkidsgames.com/games/continentNames/default.htm#
Continents • the continents are merely the crust exposed above sea level • the solid surface of the Earth below sea level is also crust. • the crust is broken into pieces which are called "plates." • The continents are the exposed portions of the Earth's plates. • However, some continents may be composed of the exposed sections of more than one plate. Therefore "continent" does not equal a plate.
Figure 2. Map showing Earth’s main lithospheric plates and some of the world’s earthquake occurrences (red dots).(From http://www.iris.edu/edu/onepagers/Hi-Res/OnePager2.pdf)
Powering the Movement of Plates • The driving mechanism believed responsible for plate movement is heat transfer within Earth’s interior. The source of the intense heat powering this great task is radioactivity deep within Earth’s mantle and primordial heat from Earth’s formation.
The movement of the plates is driven by convection cells in the mantle so the plates are continuously jostling against each other. Geologically, the most important things happen at plate boundaries, including most of the earthquakes, volcanos, igneous rocks, major metamorphism, and mountain building processes. Interplate regions tend to be rather boring.
. Divergent boundaries are where plates separate from each other, and magma oozes up from the mantle into the crack (a fissure volcano) making the ocean basin wider. This is known as sea floor spreading.
When a divergence occurs within a continent it is called rifting. Hot magma rises from deep within the mantle pushing up the crust and causing pressure forcing the continent to break and separate. Lava flows and earthquakes would be seen.
Sea Floor Spreading • Watch Bill Nye Video on disk
Convergent boundaries are where plates come together, but to do so one of the plates must dive below the surface into the mantle along a subduction zone. Convergent boundaries produce mountain chains of very large, explosive volcanos (composite type).
Here crust is destroyed and recycled back into the interior of the Earth as one plate dives under another. These are known as Subduction Zones - mountains and volcanoes are often found where plates converge. There are 3 types of convergent boundaries: Oceanic-Continental Convergence; Oceanic-Oceanic Convergence; and Continental-Continental Convergence.
When an oceanic plate pushes into and subducts under a continental plate, the overriding continental plate is lifted up and a mountain range is created. Even though the oceanic plate as a whole sinks smoothly and continuously into the subduction trench, the deepest part of the subducting plate breaks into smaller pieces. These smaller pieces become locked in place for long periods of time before moving suddenly and generating large earthquakes. Such earthquakes are often accompanied by uplift of the land by as much as a few meters.
When two oceanic plates converge one is usually subducted under the other and in the process a deep oceanic trench is formed. The Marianas Trench, for example, is a deep trench created as the result of the Phillipine Plate subducting under the Pacific Plate. Oceanic-oceanic plate convergence also results in the formation of undersea volcanoes. Over millions of years, however, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. Such volcanoes are typically strung out in chains called island arcs.
When two continents meet head-on, neither is subducted because the continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust tends to buckle and be pushed upward or sideways. The collision of India into Asia 50 million years ago caused the Eurasian Plate to crumple up and override the Indian Plate. After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights. Most of this growth occurred during the past 10 million years.
And, transform boundaries where plates slide past each other, ideally with little or no vertical movement. Most transform boundaries are below sea level and so not easy to see. The San Andreas fault in California is a transform boundary.
Transform-Fault Boundaries are where two plates are sliding horizontally past one another. These are also known as transform boundaries or more commonly as faults.
Most transform faults are found on the ocean floor and are generally defined by shallow earthquakes. A few, however, occur on land. The San Andreas fault zone in California is a transform fault. The San Andreas is one of the few transform faults exposed on land. The San Andreas fault zone, which is about 1,300 km long and in places tens of kilometers wide, slices through two thirds of the length of California. Along it, the Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr. Land on the west side of the fault zone (on the Pacific Plate) is moving in a northwesterly direction relative to the land on the east side of the fault zone (on the North American Plate).
divergent convergent ocean-to-continent convergence
