Dynamic Earth Project 100 75 55 Presentation Color and diagrams used to explain layer or plate boundary in a clear way Some parts of poster are unclear or rushed Poster is extremely rushed and does not look like much planning went into it. Accuracy All questions answered correctly from both parts Most questions on topic answered correctly Few questions answered correctly Completion All questions answered and at least 2 diagrams used to represent topic provided. Diagrams have caption Most questions answered and there is at least one diagram Missing questions and/or diagrams

Every student is assigned a layer of the Earth and then uses ESRT to find specific properties and the internet to find unique properties

Earth’s Interior Project

Asthenosphere (Plastic Mantle), Stiffer Mantle, Inner Core, Outer Core

Density

Pressure range

Size (thickness)

Temperature Range

What makes your layer of the earth unique or special?

Draw and label two diagrams that show something unique or special about your layer

Plate Boundary (Convergent, Divergent, Transform)

What symbol represents your type of plate boundary on the ESRT?

List three examples of places where your particular boundary is found on Earth

Draw a cross section (side view) of your plate boundary

Explain what happens at your plate boundary and why is it unique or special

## The Earth's Crust

At the very surface of the Earth is the crust, the topmost layer, made mostly out of solid silicate rocks like basalt and granite. The crust is like the icing on a cake, though not nearly so tasty. We humans live on top of the crust; you can think of us as the strawberries or gummy bears on the top of the cake. But to keep the analogy more to scale, we would be a lot closer to a sprinkle of confectioner's sugar. We're actually super tiny, compared to the size of the crust.

The crust is a ridiculously thin layer when the Earth's interior is drawn to scale. So small that it wouldn't show up on most diagrams. But despite being tiny compared to the rest of the layers, the crust can be a whopping 70 kilometers thick!

Continental crust, the crust under which the continents are built, is 10-70 km thick, while oceanic crust, or the crust under the oceans, is only 5-7 km thick. The deepest mine shaft ever built, Western Deep in South Africa, currently reaches 3.9 km, which barely scratches the surface of the continental crust. What comes to mind when you think of the word crust? Perhaps it is the time old saying," Eat your crust!" The earth's crust is a little different then the crust on a piece of bread. It is not soft and chewy, but it hard and composed of different minerals. The thin, outermost layer of the earth is called the crust. It makes up only one percent of the earth's mass. The continental crust is thicker than the oceanic crust. It can range from 25 km thick at the edges to 70 km thick near the center. The oceanic crust on the other hand is only about 7 km thick and considerably more dense. The crust and the uppermost part of the mantle make up the lithosphere, a solid region that is broken into plates. It is about 65 to 100 km thick.

## The Mantle

Underneath the crust is the mantle, the largest layer, composed of rocky oxides and silicates under high pressure. We once thought the mantle contained liquid magma, but we now know that is not the case; magma is formed only in certain locations, due to the high pressures and temperatures. The mantle is huge, going down to a depth of 2,500 km and is like the main part of the cake.

The mantle is sometimes split into the upper mantle and lower mantle because the upper part of the mantle moves and flows in convection currents much more easily than the lower part. Even solid rock can move and flow at these high pressures and temperatures, though it moves very slowly. The mantle is the layer below the crust. It makes up almost two thirds of the earth's mass and is about 2900 km thick. The mantel is divided into two regions, the upper and lower sections. Directly below the upper section is the asthenosphere. Heat and pressure cause a small amount of melting to occur in the asthenosphere. While still solid, the asthenosphere is able to flow. The ability of a solid to flow is calledplasticity. See "What's the matter?" for an activity to demonstrate plasticity. Since the asthenosphere is more liquid than the rest of the mantle, the broken lithosphere plates are able to "float" on it.

When the material in the asthenosphere is heated, it becomes less dense and rises. While the cooler material is more dense tends to sink. Circulating currents carry the warmer material up and the cooler material down. These circular currents in the asthenosphere are called convection currents. The circulating convection currents cause the plates to move.

## The Core

Below the mantle is the core, which is the very center of the Earth, made mostly of metals like iron. Theouter core is a liquid that flows in circles. This is like the delicious cream filling of the cake! In fact, the liquid flow of the outer core is responsible for creating the Earth's magnetic field. The inner core, on the other hand, is the solid part that is believed to contain at least 90% iron, which is like a central layer of dense pound cake. Below the mantle is the core, the center of the earth. It makes up nearly one third the mass of the earth. The core is also divided into two regions, the inner core and the outer core. From seismic or earthquake waves, scientists believe the outer core is a liquid and the inner core is a solid. The outer core is made of iron and is very dense. Scientists hypothesize that the circulation of the outer core causes the magnetic field around the earth. It is believed to be circulating in the counter-clockwise direction giving us the north pole in its present location. It switches about every million years. A record of this "switching" is recorded in the rocks both on land and in the ocean crust. See "Go west young man! But which way is north? "The inner core is made of solid iron and nickel. Many scientists believe it is kept in the solid state because of the extreme pressure from the other layers.

The outer core goes from a depth of 2,550 km down to 4,750 km, and the inner core continues to the center of the Earth at a total depth of 6,470 km.

divergent boundary

A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, lava spews from long fissures and geysers spurt superheated water. Frequent earthquakes strike along the rift. Beneath the rift, magma—molten rock—rises from the mantle. It oozes up into the gap and hardens into solid rock, forming new crust on the torn edges of the plates. Magma from the mantle solidifies into basalt, a dark, dense rock that underlies the ocean floor. Thus at divergent boundaries, oceanic crust, made of basalt, is created.

Convergent Boundary

When two plates come together, it is known as a convergent boundary. The impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench. A chain of volcanoes often forms parallel to the boundary, to the mountain range, and to the trench. Powerful earthquakes shake a wide area on both sides of the boundary.

If one of the colliding plates is topped with oceanic crust, it is forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into new crust. Magma formed from melting plates solidifies into granite, a light colored, low-density rock that makes up the continents. Thus at convergent boundaries, continental crust, made of granite, is created, and oceanic crust is destroyed.

transform plate boundary

Two plates sliding past each other forms a transform plate boundary. Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. As the plates alternately jam and jump against each other, earthquakes rattle through a wide boundary zone. In contrast to convergent and divergent boundaries, no magma is formed. Thus, crust is cracked and broken at transform margins, but is not created or destroyed.