# data[].attributes.body
the smartest dinosaur

# data[].attributes.body
terrestrial plants increased in diversity, leading to more complex ecosystems

# data[].attributes.body
The oldest eukaryotic fossil. This organism has an appearance of a type of algae.

# data[].attributes.body
The early Cambrian period is where two jawless fish with a primitive vertebrates

# data[].attributes.body
marked the end of the dinosaurs.

# data[].attributes.body
the cave men were the first humans

# data[].attributes.body
Creatures that were alive during the Paleozoic era that have now died out. They are a group of extinct arthropods

# data[].attributes.body
Oxygen gas produced by the cyanobacteria finally started to accumlate in the atmosphere.

# data[].attributes.body
It was the biggest extinction losing 56% genera and 96% of species.

# data[].attributes.body
A place where life first formed and continues to form

# data[].attributes.body
The Devonian Period is known as the “Age of Fish” because the oceans teemed with life

# data[].attributes.body
they used to be all diffrent sizes from a half a meter to a lot more meters

# data[].attributes.body
Earth was formed from the accretion of interstellar dust. During accretion, the growing mass, called proto-Earth, was compressed by gravity, causing an increase in temperature. (Sorry for the picture it was the only good one I found.)

# data[].attributes.body
chloroplasts resulted from a symbiotic event

# data[].attributes.headline
Formation of Earth, Volcanos, Moons, etc.

# data[].attributes.subject
Formation of Earth, Volcanos, Moons, etc.

# data[].attributes.attachment_link.readable_text
Hadean Eon, informal division of Precambrian time occurring between about 4.6 billion and about 4.0 billion years ago. The Hadean Eon is characterized by Earth's initial formation-from the accretion of dust and gases and the frequent collisions of larger planetesimals-and by the stabilization of its core and crust and the development of its atmosphere and oceans. Throughout part of the eon, impacts from extraterrestrial bodies released enormous amounts of heat that likely prevented much of the rock from solidifying at the surface. As such, the name of the interval is a reference to Hades, a Greek translation of the Hebrew word for hell.

Earth's surface was incredibly unstable during the early part of the Hadean Eon. Convection currents in the mantle brought molten rock to the surface and caused cooling rock to descend into magmatic seas. Heavier elements, such as iron, descended to become the core, whereas lighter elements, such as silicon, rose and became incorporated into the growing crust. Although no one knows when the first outer crust of the planet formed, some scientists believe that the existence of a few grains of zircon dated to about 4.4 billion years ago confirm the presence of stable continents, liquid water, and surface temperatures that were probably less than 100 °C (212 °F). Since Hadean times, nearly all of this original crust has subducted from the movements of tectonic plates, and thus few rocks and minerals remain from the interval. The oldest rocks known are the faux amphibolite volcanic deposits of the Nuvvuagittuq greenstone belt in Quebec, Canada; they are estimated to be 4.28 billion years old. The oldest minerals are the aforementioned grains of zircon, which were found in the Jack Hills of Australia.

Considerable debate surrounds the timing of the formation of the atmosphere as well as its initial composition. Although many scientists contend that the atmosphere and the oceans formed during the latter part of the eon, the discovery of the zircon grains in Australia provide compelling evidence that the atmosphere and ocean formed before 4.4 billion years ago. The early atmosphere likely began as a region of escaping hydrogen and helium. It is generally thought that ammonia, methane, and neon were present sometime after the crust cooled, and volcanic outgassing added water vapour, nitrogen, and additional hydrogen. Some scientists state that ice delivered by comet impacts could have supplied the planet with additional water vapour. Later, it is thought, much of the water vapour in the atmosphere condensed to form clouds and rain that left large deposits of liquid water on Earth's surface.

Archean Eon Encyclopædia Britannica, Inc. Source: International Commission on Stratigraphy (ICS)

The Moon is also thought to have formed during the Hadean Eon, and several theories of the Moon's origin have been posited. The leading theory asserts that a collision between Earth and a celestial body the size of Mars ejected material that eventually coalesced into the Moon.

Get exclusive access to content from our 1768 First Edition with your subscription. Subscribe today

John P. Rafferty

Learn More in these related Britannica articles:

# data[].attributes.attachment_link.description
Hadean Eon, informal division of the Precambrian occurring between about 4.6 billion and about 4.0 billion years ago. It was the time of Earth's initial formation-the accretion of dust and gases, collisions with larger bodies, the stabilization of its core and crust, and the rise of its atmosphere and oceans.

# data[].attributes.body
humans are the dominate form of life on earth nowadays

# data[].attributes.body
Life left chemical traces!