Vocabulary
Strata
What is the age of a rock compared with the ages of other rocks?
Relative Age
What is the official record of Earth's geologic events and life form evolution?
Geologic Time Scale
Earth
The time of single-celled life and few fossils occurred during which era?
Precambrian
The record of the geologic events and the evolution of life forms as shown in the rock and fossil records.
Geologic Time Scale
What law says that in undisturbed rock layers, the oldest layer is on the bottom?
Law of Superposition
What units of geologic time are eras subdivided into?
Which formed first, vertebrates or invertebrates?
What two things do geologists mostly study to develop the geologic time scale?
Rock Layers and Fossils
Animals without backbones.
Invertebrates
What type of dating gives the actual number of years old a rock is?
Absolute Dating
What is our current geologic era where mammals became the dominant land animals?
Cenozoic Era
What was the sudden death of many living things called?
Mass Extinction
The bottom rock layer is youngest or oldest?
Oldest
An event during which many types of living things became extinct.
Mass Extinction
What is a break in the rock record caused by erosion or missing rock layers?
Unconformity
Is the geologic time scale a model of the RELATIVE or ABSOLUTE order of events?
What period in history was it when large sheets of ice began to appear on Earth's surface and Earth's climate continued to cool?
Ice Age
Magma that pushes into layers of rock below the surface forms an extrusion or intrusion?
Intrusion
The age of a rock compared to the ages of other rocks.
Relative Age
What is the method using the decay of radioactive elements to determine the absolute age of a rock?
Radiometric Dating
Which era covers the the largest amount of Earth's history?
Precambrian
What species increased after the mass extinction of the dinosaurs?
Mammals
When rock layers erode, an older rock surface may be exposed. Then deposition begins again, building new rock layers. The surface where new rock layers meets a much older rock surface beneath them is called a(n)...