Plate Techtonics

Plate Techtonics

1. Section 1: Earth's Interior

   •  seismic waves definition: the shock waves produced by earthquakes
   • Earth's interior made up of many layers: the crust, mantle, outer core, and inner core
   • Exploring inside Earth
     •  Using data from seismic waves and rock samples, scientists have learned Earth is made up of layers.
     • Evidence from Rock Samples
       •  scientists drilled holes and found samples of rocks that told us how about the conditions deep inside Earth and when those rocks were formed
     • Evidence from Seismic Waves
       •  The speed of the seismic waves and the paths they take reveal the structure of the planet.
   • The Mantle
     • mantle definition: the layer of hot rock that is beneath the boundary of the surface
     • Lithosephere
       • The Lithosphere is the uppermost part of mantle and crust. note: lithos means "rock" note: lithosphere is cold and brittle
     • Athenosphere
       • asthenes means "weak" softer than all other layers, but still solid.
     • Lower Mantle
       • Beneath the asthenosphere. The mantle is solid and extends all the way to the Earth's interior.
   • Journey to the Center
     • pressure definition: the force pressing on an area
     • Pressure
       • The pressure increases as you go deeper into the Earth's interior   example: as you go deeper into a swimming pool, pressure increases
     • Temperature
       •  The further you go down, the warmer the temperature is.  note: temperature increases 1 Celsius degree every 40 meters.  note: temperature ratio rapidly rises every several tens of kilometers
   • The Crust
     • crust definition: the layer of rock that forms Earth's outer skin
     • The crust is as thick as 5-40 kilometers thick. Beneath mountains, crust could be 70 kilometers thick. crust beneath ocean is called oceanic crust. Continental crust forms continents and consists mainly of rocks such as granite.
   • The Core
     • note: inner core and outer core are 3486 kilometers thick
     • Outer Core and Inner Core
       • Outer core is a layer of molten that extends down to the core and surrounds the inner core. Inner core is a dense ball of solid metal note: extreme pressure squeezes metal so much, they cannot spread to and transform to liquid
       • Both parts of the core consist of of iron and nickel. Later studies show that the core also contains oxygen, sulfur, and silicon
     • Core and Earth Magnetic Field
       • Scientists believe the liquid outer core creates Earth's magnetic field.

2. Convection and the Mantle

   • Types of Heat Transfer
     • Density definition: the measure of how much mass there is in a volume of substance
     • Radiation
       • Radiation definition: The transfer through energy in space. forms of radiation are sunlight and open fire or flame Radiation takes place with no direct contact between a heat source and an object.
     • Conduction
       • conduction definition: heat transfer within a material or between materials that are touching.
       • when a heated particle touches an object in this process, the object heats up as well. This is why when you touch something hot, you can feel the warmth. Conduction is responsible for this heat transfer
     • Convection
       • convection definition: heat transfer by the movement of currents within a fluid. The process of convection begins with heated particles. The particles move faster and spread apart in result of this heat. Fluid density decreases, but then when the particles move slower, i gets compacted and heated up again. This process continues.
   • Convection Currents
     • Convection currents definition: the flow that transfers heat withing a fluid.
   • Convection Currents in Earth
     • In Earth, rocks in the lower mantle is hotter and therefore less dense than the rock above it. As a result, solid mantle rocks rises slowly from the bottom of the mantle toward the top. Then i cools and sinks back down.

3. Drifting Continents

   • Continental Drift
     • continental drift definition: The continents that slowly move over Earth's surface Pangaea definition: word meaning "all lands" to describe the merged continents 300 million years ago. fossil definition: any trace of an ancient organism that has been preserved in rock
     • Evidence from land features
       • Scientists found evidence that the same mountains and other features appear on different continents
     • Evidence from Fossils
       • Scientists found that fossils of the same plants on different continents.
     • Evidence from Ancient Climate Zones
       • Scientists have found fossils of tropical plants on Antartica which suggests it was once closer to the equator. This idea supports Wegener's theory on continental drift.
   • Wegener's Hypothesis
     • Wegener's idea rejected because was unable to identify the cause of continental drift. Also rejected because it contradicted idea about how mountains form.
     • Wegener's idea was later reapproved because of later studies supporting his idea. He also explained that if their original hypothesis of mountains was correct, mountains should form all over Earth. However, mountains have only been found to occur in narrow bands along the edges of continents note: folding continents push up huge mountains

4. Sea Floor Soreading

   • Mid-Ocean Ridges
     •  mid-ocean ridge definition: an undersea mountain chain that is part of a long system of mountains that winds beneath Earth's oceans.  sonar definition: a device that bounces sound waves off underwater objects and then records the echoes of these sound waves.
     • Mid-ocean ridges extend to all oceans and most of the mountains in mid-ocean ridges are hundreds of meters of water down.
   • What is Sea Floor Spreading?
     • Sea-floor spreading definition: A process that continually adds new material to the ocean floor.
     •   Process of sea-floor spreading starts at mid-ocean ridges, where is forms cracks in the oceanic crust. Next, molten material erupts while older rock moves outwards on both sides of the ridge. Molten cools and forms a new strip of solid rock in the center of the ridge
     • As a result of sea-floor spreading, scientists believe that there is such a thing as continental drift
   • Evidence for Sea-Floor Spreading
     • Evidence from Molten Material
       • Scientists have found new material is indeed forming along mid-ocean ridges.
       • Scientists found proof by strange rocks that could have only formed from molten material hardening quickly under water. the rocks also show that this has happened over and over again.
     • Evidence from Magnetic Stripes
       • Scientists have found that a pattern of magnetized stripes show the reversals of magnetic poles over the years.The magnetized stripes were made by sea-floor spreading
     • Evidence from Drilling Samples
       • Drilling samples show that rocks were older as you go farther from the ridge and the youngest rocks are in the center of the ridge. This shows that sea-floor spreading has taken place
   • Subduction at Trenches
     • The Process of Subduction
       • subduction definition: The process by which the ocean floor sinks beneath a deep-ocean trench and back into the mantle
       • Subduction and sea-floor spreading work hand-in-hand to move the ocean floor. The new ocean floor is warm, so it moves away from the mid-ocean ridge and toward a trench, where it gets pulled in and sinks.
     • Subduction and Earth's Oceans
       • note: subduction and sea-floor spreading can completely renew the ocean by 200 million years. Earth's Pacific ocean is shrinking because subduction in deep ocean trenches occurs faster than a new crust can be added. Earth's Atlantic Ocean is spreading because it only has a few trenches and sea-floor spreading is occuring.

5. The Theory of Plate Techtonics

   • plates definition: cracks in the lithosphere that break into separate sections. plate tectonics definition: the plates below Earth's surface that  shift and change the Earth's surface.
   • How Plates Move
     • scientists believe convection currents in mantle is major cause of plate motion. plate techtonics work by subduction. Gravity pulling one edge of a plate down into the mantle moves the plate as well.
     • shifting plates change Earth's surface. changes include earthquakes, volcanoes, mountain ranges, and deep-ocean trenches.
   • Plate Boundaries
     • fault definition: breaks in Earth's crust where rocks have slipped past each other.
     • Spreading boundaries
       • spreading boundary definition: the place where two plates move apart. rift valley definition: A deep valley that spreads along the spreading boundary
       • most spreading boundaries occur along mid-ocean ridges where sea-floor spreading happens. note: spreading boundaries are also called divergent boundaries. spreading boundaries also occur on land.
       • when spreading boundary occurs on land, two tectonic plates slide apart and a rift valley forms.
     • Sliding Boundaries
       • sliding boundary definition: a place where two plates slip past each other, moving in opposite directions; also known as transform boundaries.
       • in sliding boundary process, crust neither created nor destroyed.
     • Colliding Boundaries
       • colliding boundary definition: the place where two plates come together or collide; also known as convergent boundary. note: density determines which tectonic plate slides on top of the other. example: marble is denser than sandstone so tectonic marble plate would sink while sandstone plate slides on top.
       • first type of collision  is when two plates made up of oceanic crust meet at a trench. denser plate of the two sinks under other plate. reason for this is ocean crust gets cooler and denser during sea-floor spreading. second type involves an oceanic plate colliding with continental plate. subduction occurs as the denser oceanic plate sinks beneath the less dense continental plate.
       • third way has two continental plates colliding. no subduction. as result, no crust sinks, but squeezes the crust into mountains.
     • Plate Motions Over Time
       • evidence shows super continents have been forming and splitting over billions of years. note: Pangea formed when Earth landmass drifted together 260 million years ago.