Presentation on theme: "Earth History Precambrian Time. Geologic Time Geologic time can be measured two ways: –Relative Time: –Relative Time: Subdivisions of the Earth's history."— Presentation transcript:
Geologic Time Geologic time can be measured two ways: –Relative Time: –Relative Time: Subdivisions of the Earth's history in a specific order based upon relative age relationships –Absolute Time: –Absolute Time: Numerical ages in "millions of years" or some other measurement
The Geologic Time Scale The geologic time scale is based on relative time, and is ALWAYS written with the oldest part at the bottom. Use your ESRT (pg 8-9) to follow along with this presentation. We will talk about/see a quick review of all of the life on the Earth during its earliest history (the Precambrian).
Divisions of Precambrian Time The Precambrian is the longest division of Earth’s history (87% of all time). There are three major subdivisions of Precambrian time. –Hadean –Archaean –Proterozoic VendianVendian
Hadean Time (4.5 - 3.8 Billion Years Ago) This is the time when the solar system was forming from a nebula. –The age of the formation of the solar system (and earth) come from the ages of the oldest meteorites. The earth formed, and was probably a hot ball of molten rock. There are no rocks (and therefore, no fossils) from Haden Time.
Archaean Time (3.8 - 2.5 billion years ago) The Earth cooled enough so that rocks could form. Earth’s atmosphere was MUCH different than it is now. –Little to no O 2 –More CO 2
The Oldest Fossils The oldest fossils are approximately 3.7 billion years old. –The first fossils: Bacteria –The only fossil found for the first billion years of biological history on the Earth are bacteria. The first bacteria were probably responsible for creating oxygen in the atmosphere through photosynthesis.
Bacteria Single-celled organisms Single-celled organisms They currently live in almost every environment on Earth’s surface today. They currently live in almost every environment on Earth’s surface today. Ancient Bacteria Modern Bacteria
Stromatolites Mounds of algae and bacteria with layers of sediment. Still found in some few areas today’s oceans –Shark Bay, Australia.
Proterozoic Time (2.5 billion to 544 million years ago) Most fossils from the Proterozoic are single-celled organisms. –Prokaryote (no nucleus) and Eucaryote (with a nucleus) cells. –Stromatolites are still very common. In the late Proterozoic (Vendian) some “soft” organisms began to appear. Most of these organisms died out at the end of the Proterozoic.