Fossils
What is the process by which most fossils form?
Living things die and their remains are buried by sediments.
Which era is known as the "Age of Reptiles," and was dominated by the dinosaurs?
Mesozoic era
Fossils are most commonly found in what type of rock?
Sedimentary
What term describes an organism that no longer exists on Earth?
Extinct
What type of fossil can provide clues about the activities of ancient organisms, such as footprints?
Trace fossils
What major event marked the end of the Paleozoic Era?
A mass extinction event
The law of superposition states that in horizontal layers of sedimentary rock, the oldest layers are located where?
At the bottom
The evolution of photosynthetic organisms about 2.5 billion years ago led to an increase in what?
Oxygen in the atmosphere
Which fossil preservation method includes organisms trapped in amber?
Preserved remains
Which period is referred to as the "Age of Fishes"?
Devonian period
What is an unconformity in geological terms?
A gap in the geologic record where some rock layers have been lost due to erosion.
What was the first life form on Earth?
Single-celled organisms
What is a carbon film fossil?
A thin layer of carbon left on rock, often from plants or soft organisms
What is the time it takes for half of the atoms in a sample of a radioactive element to decay called?
Half-life
What is the term for fossils that lived in many different areas but only for a brief period of time, helping to date rock layers?
Index fossils
What process describes the gradual change of living things over long periods of time?
Evolution
What is the fossil type that forms when dissolved minerals replace the remains of an organism, often wood?
Petrified fossil
What are the three main divisions of the geologic time scale called? Provide the term for the time division and the names of each of the eras.
Eras; Paleozoic, Mesozoic, Cenozoic
What term describes the age of a rock compared to other rocks?
Relative age
Which period saw the emergence of the first invertebrates?
Cambrian period