Do Now Tuesday, March 11, 2014 Take out your notebook / Be seated Take out your reading The Earth s Interior from yesterday If you have a highlighter, take one out In your notebook, set up TOC with Layers of the Earth and today s date Set up a new page with date and title and Essential Question: What are the layers of the Earth and how do they move?
E.Q.: What are the layers of the Earth and how do they move? Set up a diagram and pick 4 colors Please draw this diagram of a circle with three inner circles Add these labels: 1. Crust 2. Mantle 3. Outer core 4. Inner core Earth s Layers 1 2 color-code each layer s note by underlining with that color 3 4
The Layers of the Earth Don t draw this just listen! There are 4 basic layers, but there are also subdivisions to each layer As we go through these notes, colorcode them! Click on image for short video Copyright 2006. M. J. Krech. All rights reserved.
Earth s Interior How do we know about these layers? Scientists discovered these layers using seismic waves from Earthquakes.
The Four Layers basic stuff The Earth is composed of four different layers. The crust is the layer that you live on, and it is the 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!
The Crust The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans (oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust).
The Crust 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.
Crust Rock Types Both Igneous Granite Basalt Continental crust Oceanic Crust* Density = 2.6 g/cm 3 Density = 2.8 g/cm 3 *oceanic crust subducts under continental crust
Take out your notebook / Be seated Open your notebook to the Layers of the Earth NOTES Be prepared to answer: What is the least dense layer of the earth? Do Now Wednesday, March 12, 2014 What is oceanic crust made of? What is the lithosphere?
The Lithosphere The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.
The Lithospheric Plates The crust of the Earth is broken into many pieces called tectonic plates. The plates "float" on the soft, semi-rigid asthenosphere.
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 and is 1800 miles thick. The movement of the middle mantle (asthenosphere) is the reason that the crustal plates of the Earth move.
Mantle and Asthenosphere The upper/middle mantle is the asthenosphere, which is responsible for the movement of plates Composed of mostly silicon, oxygen, magnesium and iron Texture is plastic like which has the characteristic of a solid but flows like a liquid when under pressure Approx 2885 km thick Has large convection currents that drive the movement of the plates click on image
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 (nickel and iron) are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place like a solid. 800 miles thick.
200 million years ago - Scientist believe that all the land on Earth was originally connected in a super continent called Pangaea (or Pangea ) Due to the movement of chunks of lithosphere, we now that the arrangement that you see on a map click on map
Plate Tectonics Theory The Lithosphere is the Earth s crust and upper mantle Lithospheric plates are thin, rigid sections of the outermost layer of the Earth that include the crust and upper mantle. New lithosphere is created at mid-ocean spreading ridges which causes them to move apart.
Plate Tectonic Theory (cont.) The size of the Earth is not increasing, so in areas where these plates meet some sections of the plates may be lost by dissolving into the mantle. Plate Boundaries are the areas where the plates meet. Plate tectonics is study of the movement and interaction of these plates of the Earth s lithosphere
Map of Major Tectonic Plates click on map
Types of Plate Boundaries Quick Overview 1. Divergent- new crust is generated and the plates pull AWAY from each other 2. Convergent- Crust is being destroyed or uplifted and the plates move TOWARDS each other 3. Transform- where crust is neither created or destroyed and the plates that slide horizontally past each other
Divergent Boundaries There are two types of Divergent Boundaries where the crustal plates are pulling away from each other 1. Oceanic-Oceanic: Mid Ocean Ridges o This is responsible for Sea floor spreading where new crust is being made as magma rises and cools in the mid ocean ridges
Divergent Boundaries (cont.) 2. Continental- Continental Divergent When a divergent boundary cuts through a piece of land, the feature called a Rift Valley is formed. Example is Iceland where the North American and Eurasian Plates are pulling apart and the African Rift Valley Volcanoes are created in Rift Valleys as magma plumes up from the separation of the plates Iceland
Convergent Boundaries Two plates move toward each other pushing together Subduction Zone - zone where one plate subsides (goes underneath) another plate Responsible for active volcanism and deep subduction earthquakes 3 Subtypes of Convergent Boundaries: 1. Oceanic-Continental convergence - subduction 2. Oceanic-Oceanic convergence - subduction 3. Continental-Continental convergence - minimal or ancient subduction and uplifting of large mountains
Oceanic-Continental Convergence When an oceanic plate collides with a continental plate, there is a Subduction Zone A volcanic arc is created inland 100-300km from the coast Trenches are formed off the coast of a subduction zone Oceanic Crust subducts under continental crust because it is more dense Ex: Pacific Northwest and Cascade mountains
Oceanic-Oceanic Convergence When two oceanic plates converge there is a battle between basaltic crusts until one subducts Volcanic Island arcs are created 100-300km away from the plate boundary Example: Japan, Aleutian Islands Trenches are created off the plate boundary Cleveland Volcano Aleutian Islands, Alaska
Continental-Continental Convergence When two continental plates collide both are very buoyant and want to stay above each other. They battle towards each other but neither one subducts under the other Builds large mountain chains with very tall mountains No volcanoes because there is not any subduction causing melting of the plates and rising magma Ex: India collides with Asia forming the Himalayas INDIA The ancient Himalayas were volcanoes because as India was pushing towards Asia, there was an ocean between them. This caused a subduction of ocean crust resulting in volcanoes.
Do Now Wednesday, March 19, 2014 Take out your notebook Have a pencil/pen out and be ready to go! OPEN YOUR NOTEBOOK to the last notes we took on plate boundaries NOTES Retakes for test Thursday/Friday before/after school 6 th period Test back today; Field study procedure tomorrow 5 th & 6 th Ms. Edwards here on Friday
Transform Boundary Transform boundaries are where two plates slide past each other Usually a part of a system of divergent or convergent boundaries Responsible for frequent shallow earthquakes Ex: San Andreas Fault in California
Hot Spots There are several other volcanoes that are not created near a plate boundary but instead in the middle of a plate They are created when a mantle plume is super heated by the core and burns through the crust building a volcano In the case of an oceanic hotspot, the plate continues to move and the volcano moves off the hotspot, and becomes inactive and just an island. A new volcano will begin to form on the ocean floor and as it peaks above the ocean surface it will become the new active volcanic island in the chain (ex. Hawaiian Islands) In the case of a continental hotspot, the caldera moves off the hotspot and when there is a new volcanic explosion, a new caldera forms in the chain (ex. Yellowstone)
Examples of Hot Spots 1. Hawaiian Islands - The active and newest island is the big island of Hawaii, and the oldest inactive island is Kauai. Since the inactive volcanoes are no longer adding to the size of the island, the island will erode away over millions of years until it becomes a seamount where is no longer above the ocean surface. Formation over hotspot; 2. Yellowstone - this is in the middle of a continent causing large scale eruptions that form calderas or collapsed volcanoes. The continental crust is too thick to produce tall standing volcanoes from a hotspot. Yellowstone Supervolcano video; other CNN clips
Pacific Ring of Fire The area around the Pacific Plate is a subduction zone and there is a lot activity Many volcanoes and volcanic islands!
You are currently on the North American Plate We are in a subduction zone. The Juan de Fuca plate is between the Pacific Plate and the North American Plate. We are vulnerable to earthquakes from plate movement and to tsunamis that might result from them. Near Us
So, what do you remember? Please number your paper 1-5 1. How old is our Earth? 2. What are tectonic plates? 3. Which tectonic plate are you currently on and which one is subducting under you? 4. Are all plate boundaries the same? If not, how many types are there? 5. Do all volcanoes result from plate boundaries?
So, how did you do? 1. How old is our Earth? 4.6 billion years 2. What are tectonic plates? Chunks of the Lithosphere that float on the Mantle s convection currents 3. You are currently on North American Plate and the Juan de Fuca Plate is subducting under you?
So, how did you do? 4. Are all plate boundaries the same? No! If not, how many types are there? 3 Types: Convergent, divergent, and transform 5. Do all volcanoes result from plate boundaries? No, Hot Spots can form in the middle of a plate.