I enjoy exploring my backyard,

but did you know, the earth is older than even the trees that grow here?

The universe is even older than the earth!

Let's learn all about it!

Let's start off with how the universe started:

THE BIG BANG!

The Big Bang Theory is the idea how the universe expanded from a very high density and high temperature state and is still expanding even now! According to this theory and calculations, the universe is approximately 13.8 billion years old.

How old is the Earth then?

According to radiometric dating and other sources of evidence, Earth formed about 4.54 billion years ago.

So how do we measure the time of earth?

The Geologic Time Scale!

The geological time scale (GTS) is a system of chronological dating that relates the layers of rock to time, and is used by geologists, paleontologists, and other Earth scientists to describe the timing and relationships of events that have occurred during Earth’s history.

Different spans of time on the GTS are usually marked by changes in the composition of rock layers.

The largest defined unit of time is the supereon, composed of eons. Eons are divided into eras, which are in turn divided into periods,then epochs, and then ages. Geologists separate these further using "early", "mid", and "late" when referring to time, and "lower", "middle", and "upper" when referring to the rock layers.

Units of Time

Precabrian Supereon

The Precambrian Supereon spanned from the formation of Earth about 4.567 billion years ago (Ga) to about 541 million years ago (Ma). It is divided into three eons: (Hadean, Archean, & Proterozoic). Life started at this time, first as single-celled organisms before diversifying into bacteria, algae, and

multi-cellular life.

Phanerozoic Eon

Paleozoic Era

The Phanerozoic Eon covers from

541 million years ago to today!

The Paleozoic Era is the earliest (and longest) era in the Phanerozoic Eon and lasted from 541 to 252.17 million years ago. During this era, there was the largest and most rapid diversification of life on Earth, as well as the largest extinction event.

Cambrian Period

The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. It lasted from 541 to 485.4 million years ago.

During this time, there was the most change in life on Earth. It went to simple cellular life to complex multi-cellular organisms. Most life lived in the oceans at this time.

Ordovician Period

The Ordovician Period lasted from 485.4 to 4438 million years ago. Most life still flourished in the ocean, though the end of this period is marked by the Ordovician-Silurian mass extinction.

The first vertebrates evolved at this time. Until then, all life had been without a distinct backbone. Mollusks and arthropods do distinctly well, dominating the oceans.

Silurian Period

The Silurian Period was from 443.8 to 419.2 million years ago. This period started off recovering from the Ordovician-Silurian mass extinction, which wiped out 60% of marine species. Jawed and bony fish took their place, along with muli-cellular life finding its way on land.

Devonian Period

The Devonian Period ranged from 419.2–358.9 million years ago. Life diversified on land, creating forests habituated with arthropods. the ancestors of all four-limbed vertebrates started walking on land, but still were tied to the water. Fish ruled the waters so well, this period is sometimes called the Age of Fish.

Carboniferous Period

The Carboniferous Period spans 358.9–298.9 million years ago. Life on land was well-established by now. Amphibians were the dominant land vertibrates. Arthropods were also very common and much larger than they are today because of the oxygen rich atmosphere. It is from this time that we get most of our coal and oil.