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Copy of Layers of the Earth
Transcript of Copy of Layers of the Earth
Layers of the Earth
Hello Everyone! Today we are going to dissect our planet, the Earth. We will begin with the very center of the Earth, which we call the Earth's core. After that we will examine the layer that surrounds the Earth's core, called the mantle. Once we see what is happening in the Earth's mantle we will take a look at the Earth's crust. These three layers of the Earth have many sub-layers categorized within the Earth's core, mantle, or crust. First we need to dissect the Earth!
Presentation made by Ryan Plouffe and Liz McCusker; ETEP 1 Section 1
The Earth's Inner Core
At the very center of the Earth is the Earth's core. Like all of the Earth's layers the composition of the core changes as the depth from the crust changes. As a result there is an inner core and an outer core. Studies in seismic energy show us that the inner core is probably composed of a metal called iron. There may also be minor traces of other elements like oxygen, silicon, sulphur, or nickel. The inner core has a shape similar to a sphere and is the densest, most compact section of the earth. The results of seismic waves created by earthquakes passing through parts of the core show us that there must be a liquid layer surrounding the core, distinct from the mantle, called the outer core. (Plummer, et al., 2007).
Solid Inner Core = 1220km
The Earth's Outer Core
After moving outwards from the center of the Earth's core we reach the Earth's outer core. As the density changes between the inner solid metal core and the outer liquid metal core we observe seismic waves moving with different speeds and patterns. Seismic energy helps us make distinctions between the outer core and the mantle because seismic waves do not pass through the outer core as freely as they do through the mantle. (Plummer, et al., 2007).
Liquid Outer Core = 2250km
The Earth's Mantle
Through use of seismic studies to observe the Earth's mantle we see that seismis energy passes through the solid rock mantle differently than the Earth's rocky crust. The mantle is made of igneous rock that contains peridotite, as well as traces of olivine and pyroxene, but lacks feldspar. Although the mantle is solid rock patches and intrusions of magma create liquid pockets. As we move through the mantle, away from the core and towards the crust, various characteristic distinctions create subcategories of the mantle. The asthenosphere and lithosphere create a transition between the solid rock mantle and the crust. (Plummer, et al., 2007).
Igneous rock Mantle = 2900km
The Core-Mantle Boundary
Between the Earth's core and mantle there is a zone in which seismic waves have drastically low velocity rates. Scientists believe that this boundary between the core and the mantle is created by reactions between iron alloys from the outer core and silicates from the mantle. These reactions create an area between the core and the mantle that consists of melted iron silicates. (Plummer, et al., 2007).
Crust thickness = 7km - 70km
Approximately 200km below the surface of the Earth the asthenosphere begins to act as one boundary between the Earth's mantle and the crust. Seismic readings detect variations between the composition of the mantle, asthenosphere, and the rest of the crust. There is debate regarding the depth and existence of the asthenosphere under continents, but scientists agree that this layer exists under the oceans. It is regarded as a crystal-and-liquid slush that has melting rocks which may act as a lubricanting layer between the solid rock mantle and the brittle lithosphere. (Plummer, et al., 2007).
The lithosphere is the layer of the Earth's crust that rests on top of the semi-liquid layer, the asthenosphere. This layer of the Earth interacts with the Earth's surface through the plate tectonic theory. Tectonic plates are enormous slabs of rock that glide on top of the asthenosphere and construct the lithosphere. The plates are connected like a jigsaw puzzle and when they move they create earthquakes. When tectonic plates move alongside each other with reletive ease it results in small earthquakes. In situations where a lot of tenstion builds between two plates prior to movement large earthquakes result. The tectonic plates in the lithosphere take thousands of years to be created by magma plumes that rise from chambers within the mantle. Once this magma reaches the lithosphere it cools while pushing through pre-existing crust. (Plummer, et al., 2007).
Types of Tectonic Plates
The magma that rises from the Earth's mantle creates tectonic plates on the top layer of Earth's crust. Magma that continuously pushes through an oceanic plate creates oceanic plates as the magma reaches the surface and cools. Underwater mountain ranges result when magma pushes through oceanic crust. Oceanic divergence, exemplified by the Mid-Atlantic Ridge shown in the picture below, provides the force needed for oceanic plates to collide with continental plates. When plates converge one of three possibilities happen;
1) The oceanic plate submerges below the continental plate and adds to the magma plume that is creating the continental plate,
2) Two continental plates converge and neither submerges, creating mountain ranges like the Himalayas in south-east Asia or,
3) One oceanic plate submerges under another ocenanic plate, creating volcanic island arcs like Alaska's Aleutian Arc shown below. (Plummer, et al., 2007). For a real-time earthquake monitor visit http://earthquake.usgs.gov/earthquakes/recenteqsww/
The Aleutian Volcanic Arc in Alaska
Representation of the Earth's inner core, outer core, mantle, and two subsections of the crust.
A magma chamber below the Earth's crust
Life on our Tectonic Plates
On top of these tectonic plates sits the thinnest layer of the Earth's crust, the surface. The surface of our Earth consists of continents and oceans. The between the layers of the Earth generate many effects on the Earth's surface. Living on tectonic plates that are controlled by forces residing in the layers of the Earth creates many dangers and awe-inspiring situations that have many implications for life on Earth's surface. (Plummer, et al., 2007). In order to take a look at at some of these situations we need to glue our dissected Earth back together!
To see the International Space Station fly over the Sahara Desert Copy/Paste this link: http://commons.wikimedia.org/wiki/File:Evening_Pass_over_the_Sahara_Desert_and_the_Middle_East.ogv
into an Internet address box to see a Wikimedia Commons video of the Sahra Desert, or
Individuals, while following regional copyright policies, can privately view this youtube video:
Following your regional copyright policies individually view this youtube video of a tsunami hitting Japan in 2011:
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The Earth has three categorized layers; the core, the mantle, and the crust. Earth's layers are not rigid and distinct from each other, they interact and converge into multiple subcategories like the inner and outer core and the crust's asthenosphere and lithosphere. The mechanics taking place within the Earth's layers have profound impacts on the surface of the Earth where we live. (Plummer, et al., 2007). With an understanding of the interactions between the Earth's layers and tectonic plates our next lesson will focus on the interactions between natural environments and life on the surface of the Earth.
Plummer, C., Carlson, D., McGreary, D., Eyles, C., Eyles, N. (2007). Physical Geology & the Environment (2nd Canadian Ed.). United States: McGraw-Hill Ryerson.
British Columbia Ministry of Education (2005). Science Grade 7: Integrated Resource Package 2005. British Columbia: Ministry of Education. Retrieved from http://www.bced.gov.bc.ca/irp/pdfs/sciences/2005scik7_7.pdf
*All Photos taken from Wikimedia Commons and are copyright free.
*Videos are referenced in text to youtube or wikimedia commons.
Thank you for viewing Ryan Plouffe and Liz McCusker's Science Lesson based on the Grade 7 Earth's Layers PLO.