what is the scientific explanation of the formation of earth's layers?
Lots of theories!
http://en.wikipedia.org/wiki/Structure_of_the_Earth
and
http://www.google.com/search?hl=en&as_q=scientific+explanation+of+the+formation+of+earth%27s+layers&as_epq=&as_oq=&as_eq=&num=10&lr=&as_filetype=&ft=i&as_sitesearch=&as_qdr=all&as_rights=&as_occt=any&cr=&as_nlo=&as_nhi=&safe=images
Thanks so much!
The scientific explanation of the formation of Earth's layers can be understood through the process of differentiation. To explain this, we need to look at the early stages of Earth's formation.
According to the widely accepted scientific model known as the "nebular hypothesis," the formation of Earth began about 4.6 billion years ago from a rotating disk of gas and dust called the primordial solar nebula.
The process of differentiation started when the primordial solar nebula collapsed due to gravity, causing it to contract and heat up. As the temperature rose, the central region, or the protosun, formed, while the surrounding disk flattened into a spinning, pancake-shaped structure.
Inside this disk, solid particles called planetesimals began to form through the process of accretion. These planetesimals grew larger as they collided and merged with each other due to gravitational attraction. Over time, this aggregation produced planet-sized bodies known as protoplanets.
As the protoplanets grew larger, the heat generated by gravitational energy and radioactive decay caused their interiors to become molten. The most massive of these protoplanets, including Earth, underwent a process called differentiation.
Differentiation occurred as the molten protoplanets began to separate into layers based on their density. Density is a measure of how much mass is in a given volume. The denser materials sank toward the center, while the less dense materials floated closer to the surface. This process is known as planetary stratification.
On Earth, the differentiation resulted in the formation of three main layers: the core, the mantle, and the crust.
1. Core: The core is the innermost layer and constitutes about 16% of Earth's volume. It is primarily composed of iron and nickel, with smaller amounts of other elements. The core is divided into two regions: the inner core, which is solid due to immense pressure, and the outer core, which is liquid.
2. Mantle: Surrounding the core is the mantle, which makes up about 83% of Earth's volume. It primarily consists of solid rock, rich in iron, magnesium, and silicon. The mantle is further divided into the upper mantle and lower mantle, with the boundary known as the transition zone.
3. Crust: The crust is the outermost layer of Earth, accounting for less than 1% of its volume. It is composed of lighter rocks and minerals, such as silicon, oxygen, aluminum, and various other elements. The crust is divided into two types: the continental crust, which is thicker and less dense, and the oceanic crust, which is thinner and denser.
This differentiation process, driven by density and heat, enables the formation of distinct layers within Earth's structure. Scientists have gained knowledge about Earth's interior through various methods, including seismic waves, laboratory experiments, and studies of meteorites.
In conclusion, the scientific explanation of Earth's layer formation revolves around the concept of differentiation, where the denser materials sink towards the core, while less dense materials float towards the surface, resulting in the formation of distinct layers - the core, mantle, and crust.