The Earth formed 4.54 billion years ago from a solar nebula. Its early atmosphere was toxic and volcanic activity and asteroid impacts were common. One large impact is believed to have formed the Moon. Over billions of years the planet cooled and developed tectonic plates and a stable crust allowing liquid water and the first life. The atmosphere gradually gained oxygen as photosynthetic life evolved. Multicellular life diversified in the Phanerozoic Eon starting over 500 million years ago, though many species died out in extinction events like the one that ended the Cretaceous Period.

1. History and formation of the Earth
Presentation #2
Juan Sebastián Rodríguez Cubillos
Biology L2 project
9-A

2. History in general:
• The history of the Earth concerns the
development of the planet Earth from its
formation to the present day. Nearly all
branches of natural science have contributed
to the understanding of the main events of
the Earth's past. The age of Earth is
approximately one-third of the age of the
universe. An immense amount of biological
and geological change has occurred in that
time span.

3. History in general:
• Earth formed around 4.54 billion years ago
by accretion from the solar nebula. Volcanic outgassing
probably created the primordial atmosphere, but it
contained almost no oxygen and would have been toxic
to humans and most modern life. Much of the Earth
was molten because of extreme volcanism and
frequent collisions with other bodies. One very large
collision is thought to have been responsible for tilting
the Earth at an angle and forming the Moon. Over
time, the planet cooled and formed a solid crust,
allowing liquid water to exist on the surface.

4. Geologic clock:

5. Geologic time scale:

6. First continents:
• Mantle convection, the process that drives
plate tectonics today, is a result of heat
flow from the Earth's interior to the Earth's
surface.It involves the creation of
rigid tectonic plates at mid-oceanic ridges.
These plates are destroyed by subduction into
the mantle atsubduction zones.

7. Oceans and atmosphere:
• Earth is often described as having had three
atmospheres. The first atmosphere, captured
from the solar nebula, was composed of light
(atmophile) elements from the solar nebula,
mostly hydrogen and helium. A combination
of the solar wind and Earth's heat would have
driven off this atmosphere, as a result of
which the atmosphere is now depleted of
these elements compared to cosmic
abundances

8. Formation of the moon:
• Earth's only natural satellite, the Moon, is
larger relative to its planet than any other
satellite in the solar system. During the Apollo
program, rocks from the Moon's surface were
brought to Earth. Radiometric dating of these
rocks has shown that the Moon is
4.53 ± .01 billion years old, formed at least
30 million years after the solar system.

9. Geologic map of north America (represented in colors
of the rocks that belong to different Earth Eras):

10. Protozoic Eon:
• The Proterozoic eon lasted from 2.5 Ga to
542 Million years ago In this time
span, cratons grew into continents with
modern sizes. The change to an oxygen-rich
atmosphere was a crucial development. The
life in this Eon mostly developed in
the prokaryotes into eukaryotes
organisms also in multicellular forms.

11. Phanerozoic Eon:
• The Phanerozoic is the current eon on Earth,
which started approximately 542 million years
ago. It consists of three eras:
The Paleozoic, Mesozoic, and Cenozoic, and is
the time when multi-cellular life greatly
diversified into almost all of the organisms
known today.

12. Mesozoic and Cenozoic Era:
• The Mesozoic era lasted from 251 Million years ago to
66 Million years ago. It is subdivided into
the Triassic, Jurassic, and Cretaceous periods. The era
began with the Permian–Triassic extinction event, the
most severe extinction event in the fossil record; 95%
of the species on Earth died out.
• The Cenozoic era began at 66 Ma, and is subdivided
into the Paleogene, Neogene, and Quaternary periods.
Mammals and birds were able to survive
the Cretaceous–Paleogene extinction event that killed
off the dinosaurs and many other forms of life, and this
is the era during which they diversified into their
modern forms.