First, we’re gonna talk about the origin of the earth. Within the nebular hypothesis, there are about six or so different steps or employed important aspects to it.
Number one is that the solar system actually evolved from an enormous rotating cloud that was called the solar nebula. Once it started to contract it made a flat disk-shaped like the shape of a cloud and it actually had a proto Sun or pre Sun that was in the middle of it.
The formation of Earth’s layered structure during the origin of the earth
Born out of gas and dust about 4.56 billion years ago, earth has had a dramatic history. Scientists have attempted to reconstruct its earliest stages from evidence preserved in meteorites and the earth itself as well as direct observations of distant stars and nebulae.
But our knowledge of events in this remotest part of our planet’s past remains incomplete. The solar nebula was initially a vast but dense cloud of cold gas and dust.
As the slowly rotating solar nebula began to contract and therefore spin faster the cloud condensed into a disc with a dense extremely hot luminous center and diffuse outer region.
The increasing speed of rotation condensed the icy gas and dust into rings within the protoplanetary disk. Colliding particles of dust and ice clumped together and their increasing gravity attracted yet more material forming planetesimals.
Those planetesimals nearest the protosun consisted of the most heat-resistant and beyond. Here planetesimals made of rock and ice grew large enough to attract and be enveloped by deep clouds of gas.
The four gas giants were formed and shortly afterward the protosun became a gas and other unaccreted material still remained in the protoplanetary disk. Most were blown away by radiation generated by nuclear fusion in the sun.
The remaining planetesimals formed the vast and distant orc cloud of comets. At the edge of the solar system according to the most widely accepted rocks and ice shared the same orbit around the developing sun.
Earth’s moon, has a highly cratered surface interspersed with dark lava fields. These impact craters all resulted from the same phase of intense meteorite bombardment as that suffered by earth and which lasted until about 3.5 billion years ago.
The earliest known moon rocks have been reliably dated at about 4.5 billion years old indicating that earth’s satellite was formed not long after earth itself.
Most astronomers agree with the giant impact theory with the young earth tore away a huge amount of its surface. Continuous heavy meteorite bombardment over the following billion years left the moon’s rocky surface severally cratered a period of volcanic activity then followed and lava oozed out of cracks in the crust to fill low-lying craters.
The lava solidified forming the moon’s vast dark maria which are still visible from the earth today. The intensity of the field fluctuated but is sufficient to align tiny iron-rich particles as if they were compass needles within certain rocks formed at the earth’s surface.
Because of this some solidified lavas and other rocks provide a record of the field’s polarity. When they were originally formed measurement of these fossil or paleomagnetic fields has revealed a chronological history of earth’s polarity.
Reversals luminous aurorae appear in the polar night skies when the earth’s magnetic field traps charged particles carried from the sun by the solar wind. Atmospheric gas particles produce a spectrum of colors.
Earth’s present oxygen-rich atmosphere differs greatly from its original atmosphere which consisted of the light gases hydrogen and helium and other volatile gases.
However, in the latter stages of the sun’s formation, this first atmosphere is blasted away by a surge of solar wind. The continuous stream of atomic stable atmosphere as the earth continued to evolve and develop intense volcanic activity expelled vast amounts of volatile gases known as outgassing.
This process released abundant nitrogen is believed to have slowly increased as microorganisms converted carbon dioxide to oxygen via photosynthesis.
Clouds of water vapor condensed and precipitated forming surface water and the first ocean’s solar system. And having abundant surface water that is being constantly recycled between its atmosphere adds to terrestrial water bodies such as seas, lakes, and oceans.
Today around two-thirds of the earth’s surface is covered with seawater. Interactions between the oceans and atmosphere are vital or maintaining the some of the earth’s oldest rocks are pillow lava from western Greenland.
Many of which are up to 3.8 billion years old and were formed by underwater eruptions. The early ocean waters reacted with carbon dioxide from the atmosphere to deposit calcium and magnesium carbonates.
As limestones weathering of rocks on the first continental landmasses also leached soluble salts into seawater existed around 3.5 billion years ago coral reefs are present-day biodiversity hot spots.
The ocean’s equivalent of tropical rainforests is the largest living structure on earth even the skeletons and shells of their inhabitants build up the seabed.
Altering the underwater environment both biologically and physically many living organisms record daily, monthly and seasonal growth cycles.
By the changing rates of growth in their shells and skeletons, coral, for example, deposits a new layer of limestone every day, and it is particularly influenced by lunar monthly growth cycles.
By studying fossil corals from the early Devonian period there were probably 410 days in a year during this part of earth’s history. Since earth’s orbit around the sun has remained constant the Devonian day must have been shorter just 21 hours.
We know that Earth has a different layered structure. As it was increasing the iron and nickel would begin to sink towards the center. Lighter rocky components would actually float outwards towards the surface.
Then we even had a gaseous material that escaped the Earth’s interior and produced our primitive atmosphere. At some point or another most of us have probably been involved in looking at layered liquids.
Earth is about 4.6 billion years old. If all the planets in our solar system formed at about the same time how old would you expect Mars to be? Any thoughts?
Probably about the same amount of time right. Same with Jupiter. same with any else that would be considered forming in our solar system. So it’s gonna be roughly 4.6 billion years old now.
Earth’s internal structure
We have a layered earth system and it can be divided up in two different ways. First, we’re gonna talk about composition. We’ll start with the crust. The crust is a thin rocky outer skin to the earth. This is subdivided into two divisions. Oceanic and continental crust.
The oceanic crust is just roughly seven to five kilometers thick. In most areas, it will be composed of a dark igneous rock that we call salt.
So that’s gonna be in your igneous rock. This is anywhere between a hundred and eighty million years old to the modern-day. so this is a lot younger and roughly the density is three grams per cubic centimeter. This is gonna be the denser of the two types of crust.
Continental crust
It is between 35 and 40 kilometers. 25 miles thick. The composition consists of a lot of different rock types and it is 4.4 billion years old or less and it is less dense at about 2.7 grams per centimeters cubed.
Mantle
This is over 82% of all of Earth’s total volume. Earth’s internal structure is defined by physical properties. Temperature, pressure, and density will gradually increase with depth into the Earth’s interior surface. So on average for about every 70 feet that you go down inside the earth, the temperature is gonna increase roughly 1 degree Fahrenheit.
Lithosphere
This consists of the crust and the uppermost part of the mantle. It’s a relatively cool, rigid shell and it can be on average about a hundred kilometers thick but in some areas maybe all the way up to 250 kilometers.
So if you’re in the ocean it’s gonna be less thick versus if you’re under an old mountain range. The mesosphere or the lower mantle is between 660 and two thousand nine hundred kilometers thick. So not a lot of information that we really need to know about the mesosphere.
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Next is the outer core which is the liquid layer and we have a convective flow of the metallic iron-rich metals that generate the Earth’s magnetic field.
The inner core
This is strong due to the high pressures and this is the solid layer. The chemical to physical or the mechanical structures of the earth. With the compositional layers, we have three layers. Whereas the mechanical layers, you’re going to get five.