10 - History of Earth and Its Life Forms Flashcards
This deck delves into Earth's past, using rocks and fossils to understand geologic time, major events, and the evolution of life. (46 cards)
Define:
principle of uniformitarianism
The idea that geological processes today also operated in the past.
The same geological processes we observe today, such as erosion and sedimentation, have been occurring in the same manner throughout Earth’s history.
Identify:
Who developed the principle of uniformitarianism?
James Hutton
James Hutton was a Scottish geologist, often referred to as the Father of Modern Geology. His observations and theories laid the groundwork for understanding Earth’s geological processes and history.
Explain:
Why do rocks provide a record of Earth’s history?
They preserve evidence of past environments, events, and life forms.
Rocks hold fossils, mineral deposits, and layers that document Earth’s changes over millions of years.
Explain:
What is the role of fossils in understanding Earth’s history?
They reveal past life and environmental conditions.
Fossils provide insights into evolutionary changes, serve as a timeline of biodiversity, and help reconstruct ancient ecosystems.
Define:
relative age dating
The method of determining the sequence of events without exact ages.
Relative age dating helps determine the sequence of events in Earth’s history by examining how layers and features are positioned relative to each other.
Explain:
What are the 3 main principles used in relative age dating?
- Superposition
- Original Horizontality
- Cross-Cutting Relationships
Superposition: In undisturbed layers, the oldest rocks are at the bottom, and the youngest are at the top.
Original Horizontality: Sedimentary layers are originally deposited flat, with any tilting or folding occurring later.
Cross-Cutting Relationships: A feature (e.g., fault or intrusion) that cuts through layers is younger than the layers it affects.
Identify:
What principle states that in undisturbed layers, oldest rocks are at the bottom, youngest at the top?
The principle of superposition
The principle of superposition is fundamental in geology, helping to determine the relative order of sedimentary layers by their position.
Define:
absolute age dating
The process of determining the exact age of rocks or fossils.
Radiometric methods, such as measuring isotopes like carbon-14 or uranium-238, are used to calculate precise ages.
Explain:
Why does absolute age dating use radioactive isotopes to determine the age of rocks?
Radioactive isotopes decay at predictable rates, providing reliable age estimates.
Identify:
List 3 isotopes used in radiometric dating.
- Carbon-14
- Uranium-238
- Potassium-40
Carbon-14: Used to date organic materials up to about 50,000 years old.
Uranium-238: Effective for dating rocks and minerals millions to billions of years old.
Potassium-40: Commonly used to date volcanic rocks and minerals over a wide range of ages.
True or False:
Radiometric dating is the most accurate method for determining rock ages.
True
Radiometric dating provides precise numerical ages, essential for absolute age determination.
Define:
What is half-life in radiometric dating?
The time it takes for half of a radioactive isotope to decay.
Half-life helps calculate the age of rocks and fossils using predictable decay rates.
Explain:
What are some limitations of radiometric dating?
- Contamination
- Initial Conditions
- Closed System Requirement
- Age Range Limits
- Material Suitability
Contamination: Foreign materials can alter isotope ratios, leading to inaccurate results.
Initial Conditions: Assumptions about the starting amount of isotopes may not always be accurate.
Closed System Requirement: Isotope leakage or alteration makes dating results unreliable.
Age Range Limits: Methods are effective only within specific time ranges (e.g., carbon-14 works up to ~50,000 years).
Material Suitability: Not all materials can be dated; only certain types of rocks or organic materials are usable.
Define:
radioactive decay
The process by which unstable isotopes break down into stable forms.
Radioactive decay releases energy and forms the basis of radiometric dating.
Identify:
What is the study of rock layers and their sequence?
Stratigraphy
Stratigraphy analyzes layers to reconstruct Earth’s history and correlate events across locations.
Identify:
What is a gap in the geologic record caused by erosion or non-deposition?
Unconformity
An unconformity represents missing time in the geologic record, often caused by erosion or non-deposition, and reveals past geological events.
Define:
geologic time
The vast span of time covering Earth’s history.
Geologic time divides Earth’s history into eons, eras, periods, and epochs to organize and study major events.
Identify:
What does the geologic time scale represent?
Earth’s 4.6 billion-year history.
It helps scientists study Earth’s development by grouping time based on significant changes in geology and life.
Explain:
What are the four major eons of Earth’s history?
- Hadean
- Archean
- Proterozoic
- Phanerozoic
Hadean: Formation of Earth and initial development, approximately 4.6 billion to 4 billion years ago.
Archean: Formation of the first stable continental crust and early life, approximately 4 billion to 2.5 billion years ago.
Proterozoic: Geological, atmospheric, and biological changes, including oxygen buildup, approximately 2.5 billion to 541 million years ago.
Phanerozoic: Development of diverse life forms, from the Cambrian explosion to the present, approximately 541 million years ago to now.
Identify:
What is the Phanerozoic eon known for?
The presence of abundant fossil evidence.
The Phanerozoic eon is marked by a rich fossil record, providing detailed evidence of the evolution and diversification of life on Earth.
Explain:
List the three eras of the Phanerozoic eon.
- Paleozoic
- Mesozoic
- Cenozoic
Paleozoic: Known for the emergence of early life forms, including fish, amphibians, and the first land plants.
Mesozoic: The age of reptiles, marked by the dominance of dinosaurs and the first birds.
Cenozoic: The age of mammals, characterized by their rise and diversification.
Define:
Mesozoic era
The era known as the Age of Reptiles.
It lasted from about 252 to 66 million years ago and saw the dominance of dinosaurs.
Define:
What is the Great Oxidation Event?
A period when Earth’s atmosphere and oceans gained more oxygen.
The Great Oxidation Event, around 2.4 billion years ago, marked a significant increase in atmospheric and oceanic oxygen, enabling the evolution of aerobic organisms and reshaping Earth’s environment.
True or False:
The last ice age ended about 11,700 years ago.
True
The end of the last ice age, around 11,700 years ago, marked a shift to the warmer and more stable climate of the Holocene epoch, which is the current geological epoch.