The Composition of the Earth
The Earth is divided into 3 layers
This is based on compounds that make up each layer. A compound is a substance composed of 2 or more elements. The less dense compounds make up the crust and the mantle. The densest compounds make up the core. The layers from because heavier elements are pulled towards the center of the Earth by gravity while elements of less mass are found farther from the center.
The Crust is "the outermost layer of the Earth". It can be anywhere from five to one hundred kilometers thick. It is the thinnest layer of the Earth.
Both are made mainly of the elements oxygen, silicon, and aluminum. However the denser oceanic crust has almost twice as much iron, calcium, and magnesium which forms minerals that are denser then the ones in the continental crust.
The mantle is " the layer of the Earth between the crust and the core." The mantle is much thicker than the crust and contains most of Earth's mass. No one has ever visited the mantle because the crust is too thick to drill through. Scientists must draw conclusion about the Composition and other physical properties from observations made on Earth's surface. In some places mantle rock pushes to the surface, but they can also look at the ocean floor. This is because magma from the mantle flows out of active volcanos ( on the ocean floor). Because the mantle has more magnesium and less aluminum and silicon than the crust, the mantle os denser than the crust.
The core is the central part of the Earth below the mantle. Scientists think that the Earth's core is made mostly of iron and contains smaller amounts of nickel but almost no oxygen, silicon, aluminum or magnesium.
The Physical Structure of the Earth
The Earth is divided into five physical layers, and each layer has its own set of physical properties. The Lithosphere, Asthenosphere, Mesosphere, Outer Core, and the Inner Core. The Lithosphere the outermost rigid layer of the Earth made up of two parts, the crust and the upper part of the mantle . This is divided into pieces called tectonic plates. Asthenosphere is a soft plastic. Like layer which pieces of the lithosphere move. IT is made of solid rock that flow slowly. Mesosphere is the strong lower part of the mantle. Next is the Outer Core which the liquid layer of the Earth's core. Last but not least is the inner core about 6380 km beneath the surface it is the solid dense center of the Earth.
A tectonic plate is pieces of the lithosphere that move around on top of the asthenosphere. A block of lithosphere that consists of the crust and the rigid outermost part of the mantle. All the tectonic plates make a giant jigsaw puzzle. Some major tectonic plates are the Pacific Plate, Eurasian Plate, and Australian Plate.
Mapping The Earth's Interior
When an earthquake happen, vibrations called Seismic waves are produced. Seismic Waves travel at different speeds though EArth, their speed depending on the density and composition of the material they ar passing though.
When a earthquake happens, machines called Seissmogprahs measure the times which the waves arrive at different distances from an earthquake. Seismologists can use these distances and travel time to calculate the density and teickness of each physical layer of Earth