Earth’s geosphere is one of the four main spheres of the planet, but what is the geosphere made of?
The geosphere is generally considered the outermost solid layer of Earth, extending from the planet’s surface to the top of the mantle.
The geosphere is made up of the inside layer of the planet Earth. It includes the structure and makeup of Earth’s interior, including rocks and minerals, as well as the landforms (mountains, valleys, etc.) that shape the surface of Earth.
The oceans and continents are also part of the geosphere.
Subsystems of the Earth
The Earth system is a complex one that begins with the Earth billions of years ago.
The Earth was formed due to a supernova, during which matter clumped together to form planets and other celestial bodies.
The Earth system is made up of four subsystems:
These subsystems interact in an interdependent way to prevent materials from leaving the planet or entering it.
Many physical, chemical and biological processes take place on this planet.
These processes are made possible by the composition and nature of the Earth system.
Fact: Basically, the geosphere (from Greek geo- meaning "earth" and sphere meaning "globe") is the solid ground of the Earth.
Parts of the Geosphere
Since the geosphere goes deep to the center of the Earth, what is the geosphere made up of?
The interior of the Earth is divided into three main layers: crust, mantle, and core.
The crust is the outer layer and is made up of a top layer called the continental crust and a bottom layer called the oceanic crust.
Below the crust, which you see only as of the planet’s surface, lies a primarily solid mantle but gives way to liquid in some areas.
The Earth’s mantle extends from the crust down to about 2,890 miles (4,599 kilometers) depth.
The mantle is composed mainly of PERIDOTITE rock, which in turn is principally composed of the minerals OLIVINE and TECTOSILICATE.
Beneath the mantle lies the outer core, which consists primarily of liquid iron and nickel. The core descends to a depth of nearly 4,000 miles (6,400 kilometers).
Note: The Lithosphere is generally conceived as the outermost solid layer of the Earth and can be further divided into tectonic plates.
Composition of the Geosphere
The Earth’s geosphere is made up of different layers and different materials and varies in composition, density, temperature, and thickness.
It’s challenging to study these layers to know what is the geosphere made up of.
But modern technology can be used to gather data on these layers indirectly with the help of seismic waves or earthquakes.
Geosphere and Wave Action
There is a lot of seismic activity in the geosphere. Three kinds of seismic waves exist:
(1) Primary, or P-waves, which travel faster through solid material than through liquids and are the first to arrive at a seismograph;
(2) Secondary, or S-waves, which move just like P-waves but at a much slower rate; and
(3) Surface waves, which can be subdivided into Rayleigh waves, which bounce back and forth between the ground surface and the Earth’s layers beneath it, and Love waves, which begin on a fault and spread out in both directions.
Note: Seismologists and volcanologists study the components of Earth's geosphere by observing the waves induced by earthquakes and volcanic eruptions.
The Earth’s crust consists of layers that vary in thickness and composition.
The thickest layer is made up of rocks that were once part of the Earth’s mantle and includes the continental shelves found on the edges of tectonic plates.
The thinner oceanic crust forms a veneer over these areas and extends beyond them to create the ocean floor.
The crust comprises eight elements:
- magnesium, and
These are the eight elements that we use in our daily lives to produce things such as glass (silicon dioxide is used in windows) and concrete (calcium carbonate is used in building construction).
The Mohorovicic Discontinuity, or the Moho, is a seismic discontinuity located at about 30 kilometers depth in the upper mantle.
Croatian seismologist Andrija Mohorovicic discovered it soon after creating the first global seismological map of the world by studying earthquake waves’ velocity through the Earth.
The name “Moho” comes from the name of his home city, Dubrovnik.
The Moho is the transition layer between the crust and mantle.
Scientists once thought that seismic waves behaved differently as they traveled from the crust to the mantle, which is why this layer was called a “discontinuity.”
In Earth’s geosphere, a layer called the upper mantle extends down from around 100 km to just over 700 km.
There are two layers below this – the lower mantle and what’s now known as the asthenosphere.
The asthenosphere lies in between the lower mantle and upper mantle.
When examining what is the geosphere made of, it’s essential to understand that much of the Earth’s mass is in the mantle.
A lot of mass means a lot of pressure.
The asthenosphere, the portion of the upper mantle that lies below the Lithosphere, is so hot and pressurized that most rock there behaves in a plastic manner.
Molten Rocks in the Mantle
Some rigid parts of the mantle, on the other hand, float or move about slowly on this semi-molten supporting material.
The flow of large bodies of semi-molten and molten material in some mantle parts breaks up the rigid mantle into plates, which can be moved much more quickly.
This explains the phenomenon of plate tectonics. The mantle layer of the Earth is made up mainly of silicate rocks.
The mantle makes up 84% of the Earth’s total volume.
Scientists do not know a lot about the mantle. They do so by studying xenoliths.
Xenoliths are rocks that were forced into the magma as it rose or embedded in magma as it cooled.
Scientists study these rocks to understand better what the mantle contains.
Note: Both mantle sections, the asthenosphere and Lithosphere are solid but behave like melted rock due to extremely high heat.
The Gutenberg discontinuity is a foundational layer of the Earth located just above the upper mantle, which can be found at the bottom of the Lithosphere.
The name is attributed to Bavarian geophysicist Beno Gutenberg, who first discovered it in 1931.
The Gutenberg discontinuity does not remain constant because of heat flow changes in the mantle.
When heat dissipates, the molten core shrinks and moves closer to Earth’s surface, causing the Gutenberg discontinuity to migrate closer to Earth’s surface.
The core of Earth is made up mainly of iron and nickel because the outer layer of iron is in liquid form. It’s known as the outer core.
However, the inner core is solid because there’s no molten material in its center. Iron is essential to Earth’s magnetic field.
Earth’s magnetic field extends outward to protect Earth from solar winds, deflecting them and thus helping to maintain the quality of the atmosphere.
Without the magnetic field, solar winds would constantly stream toward our planet and could damage Earth’s atmosphere and all living forms.
Young Danish seismologist Inge Lehman studied the shock waves produced by earthquakes and noticed something exciting.
She observed that the waves bounced off what scientists thought was a solid boundary between the liquid outer core and the solid inner core.
This boundary is called Lehman Discontinuity.
Modern technology has immensely helped geologists unearth what is the geosphere made of, not only for academia but also to support industries that depend on the geosphere for raw materials.
The Earth formed some 4.5 billion years ago and has gone through various stages over time.
The geosphere is particularly crucial to understand since it includes the bulk of the Earth's composition.
Through technology, we get to understand our planet better to improve our living conditions on Earth.