Our earth is nothing but a mass of solid rocks heated inside and out, creating the same layer of gas that makes up the atmosphere

 The beginning of the earth

Our earth is nothing but a mass of solid rocks heated inside and out, creating the same layer of gas that makes up the atmosphere. It should be noted that the composition of the atmosphere has evolved over the years. It wasn't always like now. Water, earth, and air began to interact violently until lava erupted profusely from the Earth's interior through various fissures in the Earth's crust. All this was enriched by its transformation due to volcanic activity.

According to scientists and their studies, about 13.800 billion years ago, there was a big explosion called Big Bang. The force released at extremely fast speeds, like the speed of light, pushed this ultra-dense material in all directions. As they moved away from the center and slowed down over time, large amounts of matter accumulated and condensed in the later galaxies.

We do not know what happened in this universe in the first 9 billion years; If there are other suns, other planets, empty space or nothing. A galaxy must have formed in the middle of this period, or perhaps earlier.

Formation of Sun and Planets

Near the edge of this galaxy we now call the Milky Way, about 5 billion years ago, some matter became concentrated in a dense cloud. This situation can happened in  many points but we are  interested in this one.

A nearby star is believed to have exploded and gone supernova about 4.600 billion years ago. The shock wave from that explosion started moving the material in our early solar nebula. The cloud began to spin rapidly and flatten into a disk. Gravity concentrates most of the mass into a central sphere, while smaller masses rotate. The central mass becomes an incandescent sphere, a star, and our Sun.

As they orbit the Sun, these small masses condense to form planets and some moons. Between them there is at least a reasonable distance and sufficient volume to keep the water in a liquid state and to keep a significant gaseous envelope. Naturally, this planet is ours, on Earth.

History of Earth

After the early stages of Earth becoming a hot material, the outer layers began to solidify, but the heat inside melted them again. 

In the beginning, Earth had no atmosphere and was therefore vulnerable to meteorites. Volcanic activity is violent and ejects large volumes of hot lava. As the crust cools , the strong of the crust  increases.

This volcanic activity produces large amounts of gas, which forms a layer on the Earth's surface. Its composition was very different from today, but it was the first protective layer that allowed liquid water to appear. Earth's early atmosphere, called "atmosphere I" by some authors, was composed of hydrogen and helium, with some methane, ammonia, rare gases, and little or no oxygen.

Volcanic eruptions produce oxygen and hydrogen water vapor, which condenses as rain rises into the atmosphere. Over time, when the earth's surface cools, the water in the precipitation remains liquid in the deepest part of the earth's crust and forms an ocean and a water sphere.

Paleontology henceforth studies geological history and paleontology specializes in the study of Earth's biological history.

 Geological History of the Earth

Investigations to determine and understand the geologic history of the Earth draw data and clues from four main rock types. Each type of rock is produced by different activities in the Earth's crust:

*Erosion and transport lead to subsequent deposition and continuous production of sedimentary rock layers, compaction and lithification.

Lava flows out of the deep magma chamber and cools on the surface of the Earth's crust to form volcanic rock.

Geological structure is made up of existing rocks that have undergone various deformations.

Plutonic or magnetic activity generated within the Earth and they have influence abroad.

The division of geologic time scales in Earth's history is based primarily on changes in the forms of fossils and other materials found in successive layers. However, the first 447 to 540 million years of the Earth's crust are recorded in fossil-free rocks, meaning that only suitable fossils survive from the last 540 million years.

For this reason, scientists divide Earth's vast geologic history into two major periods: the Precambrian, which includes the Subzoic, Paleophonic, and Proterozoic, and the Phanerozoic, which reaches the actual fossil age of that era.

The discovery of radioactivity enabled geologists and paleontologists in the 19th century to hypothesize new dating methods that could determine absolute ages (in millions of years).