What is a fossil?
Mineralized bones, teeth, shells, seeds, spores, or other long-lasting parts of an organism that lived in the past
Fossils provide evidence of ancient life and its activities.
Define trace fossil.
The physical evidence from the ancient past of an organism’s activities
Trace fossils include footprints, burrows, and other signs of life.
What is the process of fossilization?
- Organism or its traces covered by sediments, mud, or ash
- Groundwater seeps into remains
- Minerals dissolved in water replace minerals in bones and other hard tissues
- Mineral particles crystallized in cavities and impressions form detailed imprints
- Sediments on top exert increasing pressure transforming remains into rock
Fossilization is a complex process that preserves the remains of organisms over time.
What is an index fossil?
A fossil that dates the layers where it is found because it came from an organism that is abundantly preserved, widespread geographically, and existed for a relatively short time
Index fossils are crucial for dating and correlating the age of rock layers.
Define radiometric dating.
A method of estimating the age of a rock or fossil by measuring the content and proportions of a radioisotope and its daughter elements
This technique is essential for determining the age of geological materials.
What is half-life?
The time it takes for half of the atoms in a sample of a radioisotope to decay
For example, the half-life of C-14 is 5730 years.
What does the ratio of C-14 to C-12 indicate?
It declines over time in an organism’s remains
This ratio is used in carbon dating to estimate the age of biological material.
What are the units of geologic time?
- Eons (500 million years or more)
- Eras (several hundred million years)
- Periods (ten to several hundred million years)
- Epochs (tens of millions of years)
- Ages (several million years)
These units help in understanding Earth’s history and the timeline of life.
What is Uniformitarianism?
The principle that geologic processes that shape Earth’s surface today are the same as those in the past
This concept contrasts with catastrophism and emphasizes gradual changes.
What does Gradualism propose?
Changes in landforms were the result of changes that occurred over a long period of time
Proposed by James Hutton in the late 1700s, it emphasizes slow, continuous processes.
True or false: Catastrophism suggests that major catastrophic events shaped Earth’s surface.
TRUE
This principle contrasts with gradualism and highlights the impact of sudden, large-scale events.
