Who was James Hutton In the late 1700s James Hutton began to question some of the ideas regarding the Earth He found fossils and saw them as evidence of life forms that no longer exist Different types of fossilized creatures were found in different layers of rock ID: 628455
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Notes Geology Chapter 2.3: Geologic TimeSlide2
Who was James Hutton?
In the late 1700s, James Hutton began to question some of the ideas regarding the Earth.
He found fossils and saw them as evidence of life forms that no longer exist.
Different types of fossilized creatures were found in different layers of rock.
He was the first person to present a hypothesis that Earth changes over time.
Wind, water, heat, and cold break down rocks, while volcanic eruptions and building up of sediment continue to form new rock.Slide3
What is uniformitarianism?
Hutton’s theory of uniformitarianism states two things:
Earth is an ever-changing place.
The same forces of change at work today were at work in the past.
Hutton’s theory is the basis of modern geology.
Some changes are gradual (like mountains forming), others are fast (like a volcanic eruption and earthquakes).Slide4
What is the Geologic Time Scale?
The Geologic Time Scale divides Earth’s history into intervals of time defined by major events or changes on Earth.
Scientists use information from fossils and radioactive dating to figure out what happened over the 4.6 billion years of Earth’s history.Slide5
How is the geologic time scale divided?
The geologic time scale is divided into eons, eras, periods, and epochs. These divisions are based on changes or events recorded in rocks and fossils.
The largest unit of time is an eon. There are 4 eons in Earth’s 4.6 billion-year history: Hadean, Archean, Proterozoic, and Phanerozoic.
Eons may be divided into eras.
Each era is subdivided into a number of periods.
Periods are further divided into epochs.
Eons → Eras → Periods → Epochs
bya=billion years ago, mya=million years agoSlide6
What is Precambrian time?
The Hadean, Archean, and Proterozoic eons together are called Precambrian time and make up almost 90% of Earth’s history.
Fossils in the Precambrian time were mostly tiny organisms that can only be seen with a microscope (bacteria and protists).Slide7
What is the Phanerozoic eon?
The Phanerozoic eon is the most recent eon, and began around 544 million years ago.
The Phanerozoic eon is divided into three eras:
The Paleozoic Era, which means “ancient life”
At the beginning, all life lived in oceans, fish with backbones developed. Towards the end, life moved onto land, reptiles and insects were common.
Ended with a mass extinction: when many different life forms all die out (or become extinct) at the same time (248 mya).
The Mesozoic Era, which means “middle life”
Also called the Age of Reptiles, because this is when dinosaurs ruled the Earth. Mammals, birds, and flowering plants also appeared.
The Mesozoic era ended with another mass extinction, thought to be caused by an asteroid hitting the Earth, throwing dust into the air and blocking sunlight, causing plants to die (65 mya).
The Cenozoic Era, which means “recent life”Slide8
What is the Cenozoic Era?
The Cenozoic era is the most recent era, began about 65 million years ago and continues today.
The Cenozoic era is also known as the Age of Mammals because it marks the time when mammals became a main category of life on Earth.
The Cenozoic era is divided into two periods: the tertiary and the quaternary.
The Quaternary period stretches from 2 million years ago to the present.
Most of the Quaternary has been a series of ice ages with much of Europe, North America, and Asia covered in ice.
Mammoths, Saber-Toothed tigers, and other giant mammals were common during the first part of the quaternary.
Fossils of the first modern humans are also from this period; they are about 100,000 years old.