If you could look inside a planet, you would quickly notice it's distinct layers. the heaviest material(metals) appear in the centre, lighter solids(rocks) occupy the middle, and less dense liquids and gases are found at the top.For planet Earth, we know these layers as the iron core, the rocky mantle and crust, the liquid ocean, and the gaseous atmosphere. More than 95 percent of the variations in composition and temperature within Earth are due to this seemingly simple layered structure. However, Earth’s interior is much more complex, sustaining what might otherwise be a lifeless cinder floating in space.In addition to Earth’s layers, small horizontal variations in composition and temperature at various depths verify that the interior of our planet is a dynamic place. The rocks of Earth’s mantle and crust are constantly moving because of plate tectonics. In addition, material is continuously recycling between the surface and the deep interior. It is also from Earth’s deep interior that the water and air of our oceans and atmosphere are replenished, allowing life to exist at the surface.
Earth's internal structure:
Earth’s interior consists of three major layers defined by their chemical composition—the crust, mantle, and core. In addition, Earth’s three compositionally distinct layers can be further subdivided into zones, based on physical properties that include whether the layer is solid or liquid and how weak or strong it is. Knowledge of both types of layers is essential to our understanding of basic geologic processes, such as volcanism, earthquakes, and mountain building.
figure1:
figure show's that Earth’s layered structure: The properties of Earth’s layers include the physical state of the material (solid, liquid, or gas) as well as
how strong the material is—for example, the distinction between the strong lithosphere and weak asthenosphere. Studies have shown that Earth’s layers are mainly determined by density, with the heaviest materials (iron) at the center and the lightest ones (gases and liquids) on the outside.
figure show's that Earth’s layered structure: The properties of Earth’s layers include the physical state of the material (solid, liquid, or gas) as well as
how strong the material is—for example, the distinction between the strong lithosphere and weak asthenosphere. Studies have shown that Earth’s layers are mainly determined by density, with the heaviest materials (iron) at the center and the lightest ones (gases and liquids) on the outside.
Gravity and Layered Planets
If a bottle filled with clay, iron filings, water, and air were
shaken, it would appear to have a single, muddy composition. If that bottle were then allowed to sit undisturbed, the different materials would separate and settle into layers. The iron filings, which are the densest, would be the first to sink to the bottom. Above the iron would be a layer of clay, then water, and, finally, air. This is similar to what happens inside planets. At their birth, planets accumulate huge quantities of nebular debris that melts and quickly segregates into layers. The iron sinks to form the core, rocky substances form the mantle and crust, and gases rise to create an atmosphere. All large bodies in the solar system have iron cores and rocky mantles, including the predominantly gaseous bodies Jupiter, Saturn, and the Sun. The force of gravity is responsible for the layering in both the bottle of muddy water and the planets.
If a bottle filled with clay, iron filings, water, and air were
shaken, it would appear to have a single, muddy composition. If that bottle were then allowed to sit undisturbed, the different materials would separate and settle into layers. The iron filings, which are the densest, would be the first to sink to the bottom. Above the iron would be a layer of clay, then water, and, finally, air. This is similar to what happens inside planets. At their birth, planets accumulate huge quantities of nebular debris that melts and quickly segregates into layers. The iron sinks to form the core, rocky substances form the mantle and crust, and gases rise to create an atmosphere. All large bodies in the solar system have iron cores and rocky mantles, including the predominantly gaseous bodies Jupiter, Saturn, and the Sun. The force of gravity is responsible for the layering in both the bottle of muddy water and the planets.
Mineral Phase Changes
Another effect of gravity is that density changes occur not only between layers but also within layers; this happens because materials may compress when they are squeezed. Rocks in the upper mantle have a density of about 3.3 grams per cubic centimeter (g/cm3). However, the density of these same rocks when taken to the base of the mantle increases to 5.6 g/cm3, nearly twice the original density. This increase in density occurs partly because atoms shrink and occupy less space when subjected to immense pressure. In addition, atoms compress at various rates, and it is easier to compress negative ions than positive ions. Negative ions have more electrons than protons and tend to be “fluffier” than positive ions. For example, when rocks are squeezed, the negative ions (such as O2) compress more easily than the positive ions (such as Si4 and Mg2), so the ratios of ionic sizes change. As these ratios change, the structure may eventually become unstable, and the atoms rearrange into a more stable and denser structure. This is called a mineral phase change. For example, at depths between 300 and 400 kilometers, the intense pressure of the overlying rocks causes the mineral olivine to become unstable. As a result, the atoms in olivine rearrange into a denser and more stable crystalline structure. The increase in density of mantle rocks is due both to the compression of existing minerals and to the formation of new “high-pressure” minerals.
Another effect of gravity is that density changes occur not only between layers but also within layers; this happens because materials may compress when they are squeezed. Rocks in the upper mantle have a density of about 3.3 grams per cubic centimeter (g/cm3). However, the density of these same rocks when taken to the base of the mantle increases to 5.6 g/cm3, nearly twice the original density. This increase in density occurs partly because atoms shrink and occupy less space when subjected to immense pressure. In addition, atoms compress at various rates, and it is easier to compress negative ions than positive ions. Negative ions have more electrons than protons and tend to be “fluffier” than positive ions. For example, when rocks are squeezed, the negative ions (such as O2) compress more easily than the positive ions (such as Si4 and Mg2), so the ratios of ionic sizes change. As these ratios change, the structure may eventually become unstable, and the atoms rearrange into a more stable and denser structure. This is called a mineral phase change. For example, at depths between 300 and 400 kilometers, the intense pressure of the overlying rocks causes the mineral olivine to become unstable. As a result, the atoms in olivine rearrange into a denser and more stable crystalline structure. The increase in density of mantle rocks is due both to the compression of existing minerals and to the formation of new “high-pressure” minerals.
No comments:
Write comments