Earth: From crust to core Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. This is only the planet which has life in it.
Nobody has journeyed to the center of the Earth to see what it is like. However, scientists using seismic waves have developed models showing what the Earth is made of and the thickness of the different layers. This is discussed in the next slide…
The history of the earth
In the very beginning of earth's history, this planet was a giant, red hot, roiling, boiling sea of molten rock - a magma ocean. The heat had been generated by the repeated high speed collisions of much smaller bodies of space rocks that continually clumped together as they collided to form this planet. As the collisions tapered off the earth began to cool, forming a thin crust on its surface. As the cooling continued, water vapor began to escape and condense in the earth's early atmosphere. Clouds formed and storms raged, raining more and more water down on the primitive earth, cooling the surface further until it was flooded with water, forming the seas.
Earth is divided in 3 parts
- outer core
- Inner core
Structure of the earth Outer core inner core Mantle Crust
C r u s t
The crust is the Earth’s thin outer rind. It accounts for only 0.4 percent of the Earth's mass. The boundary between the crust and the mantle is called the Mohorovicic Discontinuity or MOHO for short.
Crust , the upper layer of the Earth, is not always the same. Crust under the oceans, called oceanic crust, is much thinner than continental crust. It is only about 5 km thick while continental crust can be up to 65 km thick. Also, the two types of crust are not made of the same materials. Oceanic crust is made of a denser collection of minerals than continental crust. The tectonic plates are made up of the Earth’s crust and the upper part of the mantle layer underneath. Together the crust and upper mantle are called the lithosphere and they extend about 80 km deep. The lithosphere is broken into giant plates that fit around the globe like puzzle pieces. These puzzle pieces move a little bit each year as they slide on top of a somewhat fluid part of the mantle called the asthenosphere. All this moving rock can cause earthquakes.
An illustration showing Earth crust
Beneath the crust is the mantle. The mantle is about 2900 km deep. The mantle has two parts. The upper part is solid rock. Below the solid rock, the mantle rock behaves like a very thick liquid, such as molasses. The mantle rock behaves like a liquid because of very high temperatures and pressure. Like all liquids, the rock can flow. The rock also has some properties of solid. It is an in-between phase of matter called plastic phase. A plastic material is neither a solid nor a liquid. It has properties of both solids and liquids.
The mantle is a part of an astronomical object. The interior of the Earth, similar to the other terrestrial planets, is chemically divided into layers. The mantle is a highly viscous layer directly under the crust, and above the outer core. Earth's mantle is a ~2,900 km thick (1,800 miles) rocky shell comprising approximately 70% of Earth's volume .
O u t e r C o r e
The outer core of the Earth is a liquid layer above the solid inner core. It is located from 2,890 to 5,150 km (1,800 to 3,200 mi) below the Earth's surface.
Outer core: 30.8% of Earth's mass; depth of 2,890-5,150 kilometers (1,806 - 3,219 miles) The outer core is a hot, electrically conducting liquid within which convective motion occurs. This conductive layer combines with Earth's rotation to create a dynamo effect that maintains a system of electrical currents. . .
. . .This is known as the Earth's magnetic field. It is also responsible for the subtle jerking of Earth's rotation. This layer is not as dense as pure molten iron, which indicates the presence of lighter elements. Scientists suspect that about 10% of the layer is composed of sulfur and/or oxygen because these elements are abundant in the cosmos and dissolve readily in molten iron. The outer core has a radius of ~3500 km.
Inner core Inner core
Composed mainly of iron, Earth's core consists of a solid inner core about 2,400 kilometers in diameter and a fluid outer core about 7,000 kilometers in diameter. The inner core plays an important role in the geodynamo that generates Earth's magnetic field.
The solid inner core is elastically anisotropic; that is, seismic waves have different speeds along different directions. The anisotropy has been found to change with hemisphere and with radius. In the latest work, Sun and Song describe another anomaly -- a global structure -- found within the inner core…
… A new way of measuring the composition of the core was found when the shock-waves from earthquakes on one side of the world were measured by sensors on the opposite surface.
Today, we don’t care about what we do. We throw plastic (inorganic waste) on the roads, use the natural resources without any thought in our mind. We think that the resources we get would be there forever. But, that’s a wrong thought in our mind. Dgth
This was a presentation by- 1) Paritosh V. Dayma 2) Rahul V. Ahiray - Rasbihari International school