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Precambrian and Its Many Phases
Transcript of Precambrian and Its Many Phases
Precambrian and Its Many Phases
Earth's surface changed many times during the Precambrian. In the beginning, Earth was a giant mass of magma, but it eventually cooled enough to have a stable crust. Then, water vapor in the atmosphere condensed and fell as rain, eventually covering the Earth in a giant ocean.
The Beginning of Earth
These words listed come from the Greek language or are related to something.
Precambrian: Which is named after Cambria, where rocks were first studied
Hadean eon: Greek for “hellish”
Archean eon: Greek for “ancient”
Proterozoic eon: Greek for “former life”
Why did this Period end?
The ice age or the "Snowball Earth" and the warming of Earth ended the Period. The only major extinctions is the death of all bacteria that cannot survive with high levels of oxygen. Since the oxygen level rose and carbon-dioxide levels declined an oxygen ozone layer was established, shielding the Earth's surface from harmful solar radiation.
The Precambrian made up about 85-88% of the Earth's history.
Snowball Earth describes that for millions of years the Earth was almost entirely covered in ice, stretching from the poles to the tropics.
This freezing happened over 650 million years ago in the Precambrian. Carbon dioxide from volcanoes may have saved Earth from an icy fate. The carbon dioxide heated the Earth, therefore ending "Snowball Earth".
The Precambrian lasted from 4500 MYA to 570 MYA; which is about 3,930,000,000 years.
Geological events: The oxygen-rich ozone layer is established. Without this, humans would not have evolved, let alone existed.
Plant evolutions: Chlorobionta and Rhodophyta algae form.
The Earth was formed about 4.5 billion years ago in a giant disc-shaped cloud of material that also formed the Sun. Gravity slowly gathered this gas and dust together which became asteroids and small early planets. These objects collided repeatedly and gradually got bigger, building up the planets in the Solar System, including the Earth.
Just about 50 million years after the Earth's formation, it is thought that the Moon formed due to a collision between the Earth and a Mars-sized body, called Theia.
Animal evolutions: The earliest multicelled animals that survived the Precambrian where the soft-bodied sponges, which lack organs or a nervous system. The cnidarians, which included sea anemones, corals, and jellyfish, they had sac-like bodies and a simple digestive system with a mouth but no anus. They caught food using tentacles armed with microscopic stinging cells. The third and last is the the annelids, or segmented flatworms, they had fluid-filled body cavities and breathed through their skins.
The other (less important) stuff