Vocabulary
This of a rock is its age compared to the ages of other rocks
What is relative age?
Geologists use this to determine the relative ages of sedimentary rock layers
What is the law of superposition?
Eras are subdivided into units of geologic time called these
What are periods?
An animal with a backbone
What is a vertebrate?
single and simple celled organisms
This is a record of the geologic events & the evolution of the life forms as shown in the rock & fossil records
The preserved remains of traces of living things are called these
What are fossils?
The Mesozoic era is defined by the dominance of these
What are dinosaurs?
An animal that lives part of its life on land & part of its life in water
What is an amphibian?
Index Fossils are this.
What is index fossils, usually preserved in sedimentary rock layers, are fossils of organisms that were widely distributed and lasted only for a short time geologically
Animals without backbones
What are invertebrates?
A gap in the geologic record
What is an unconformity?
This is why scientists constantly refine the geologic time scale
What is new data is discovered?
These have scaly skin & lay eggs that have tough, leathery shells
What are reptiles?
The first feathered flying creatures evolved during this era
What is the Mesozoic?
This of a rock is the number of years that have passed since the rock formed
What is absolute age?
During this, the atoms of one element break down to form atoms of another element
What is radioactive decay?
This is how the Precambrian Time is different from the other divisions of the geologic time scale
What is it is the oldest block & time & lasted much longer than the other divisions of time?
An event during which many types of living things became extinct at the same time
What is a mass extinction?
What is photsynthesis
The process in which plants convert sunlight into food creating the byproduct of oxygen
Geologists divide the time between the Precambrian & the present into 3 long units of time called these
Geologists use this to determine the absolute ages of rocks
What is radioactive dating?
This is an example of physical evidence used to organize Earth's history on the geologic time scale
What are fossils?
A vertebrate that controls its own body temperature & feeds milk to its young
Ruby and Harry were putting together a presentation about the geologic time scale to share in class. This is the purpose of the geologic time scale
What is to organize and sequence events in the history of Earth and to serve as a model for a vast amount of time covered