Transcript Earth`s Internal Structure
Earth’s Internal Structure
What’s down below us?
Earth’s Internal Structure
The Earth is made up of a variety of materials. However, it is arranged into layers. The solid materials of the Earth are separated into layers according to
composition and mechanical
properties.
Earth’s Internal Structure
Earth can be divided into 3 main
compositional layers
: (made up of different materials) Crust (outside of Earth) Mantle Core (very inside)
Earth’s Internal Structure
Layers based on physical (mechanical) properties are: Lithosphere (most outer layer) Asthenosphere Mesosphere Outer Core Inner Core
Earth’s Internal Structure
The Earth’s interior consists of a series of shells of different compositions and mechanical properties. Earth is called a
differentiated planet
because of its separation into layers. The Earth consists of internal layers of increasing
density
toward the center of the Earth.
Earth’s Internal Structure
The internal layers were produced as different materials rose and sank so that the least dense materials were at the surface and the most dense materials were in the center of the planet. Therefore,
gravity
is the force behind Earth’s differentiated planet.
Chemical Composition
Crust is the outermost compositional layer of the Earth.
Crust of the continents is distinctly different from the crust beneath the ocean floor.
Continental crust
is much thicker (up to 75km), is composed of less-dense grantic rock, is strongly deformed and includes the planet’s oldest rocks (billions of years in age).
Oceanic crust
age).
is only about 8km thick, is composed of denser volcanic rock called basalt and is comparatively undeformed by folding and is geologically young (less than 200 million years in
Chemical Composition
The
mantle
is the next major compositional layer of the Earth. It surrounds or covers the core. The zone is about 2900km thick and constitutes the great bulk of Earth (82% of its volume and 68% of its mass).
The
mantle
is composed of silicate rocks that also contain abundant iron and magnesium. Fragments of the mantle have been brought to the surface by volcanic eruptions. The mantle’s density increases with depth (being the densest where it is closest to the core).
Physical Properties
Physical properties
of a material are also known as mechanical properties. They tell us how a certain material responds to force, how weak or strong it is and whether it is a liquid or solid.
Physical Properties
The
lithosphere
(rock sphere) is the solid, strong and rigid outer layer of the Earth. It includes the crust and upper most part of the mantle. It varies greatly in thickness, from as little as 10km in some oceanic areas to as much as 300km in some continental areas.
Physical Properties
The
asthenosphere
(weak sphere) is within the upper mantle. In the asthenosphere the temperature and pressure are just right so that part of the material melts or nearly melts. Under these conditions, rocks lose much of their strength and become soft and plastic and flow slowly.
Convection currents
exist here as the rock heats, becomes less dense, rises, then cools near the lithosphere and drops back into the depths of the mantle.
Physical Properties
The
mesosphere
(middle sphere) is the region between the asthenosphere and the core. The rock here is stronger and more rigid than in the Asthenosphere. This is because the high pressure at this depth offsets the effect of high temperature.
Physical Properties
The Earth’s core has 2 distict parts: The
Inner Core:
Is solid Radius of about 1200 km Chiefly made of iron The
Outer Core
Is liquid Thickness of about 2270km (about twice of that of inner core)
Physical Properties
Earth’s core is extremely hot. Heat loss from the core and the rotation of Earth cause the liquid outer core to flow and rotate faster than the inner core. This circulation generates Earth’s magnetic flow.
Earth’s Outermost Layers
The outermost layers of the Earth are the
atmosphere, hydrosphere and biosphere.
The atmosphere
is composed of 78% nitrogen, 21% oxygen and minor amounts of other gases such as carbon dioxide and water vapour. The earliest atmosphere was much different; it was essentially oxygen free and consisted largely of carbon dioxide and water vapour. The present carbon dioxide “poor” atmosphere developed as soon as limestone began to form in the oceans, tying up the carbon. Oxygen was added to the atmosphere when plants evolved.
Earth’s Outermost Layers
The
hydrosphere
is the total mass of water on the surface of our planet. Water covers about 71% of the surface. About 98% of this water is in oceans, while only 2% is in streams, lakes, groundwater and glaciers. It has been estimated that if the Earth’s surface was smoothed out, a global ocean would cover Earth to a depth of 2.25km.
The
biosphere
is the part of Earth where life exists.