"Age of Mammals"
65 mya - present; characterized by rapid radiation of mammals
543 mya - 252 mya; rapid radiation of fish and amphibians
"Age of Reptiles"
252 mya - 65 mya; reptiles were dominant life form, ended after Cretaceous Period with mass extinction of dinosaurs
geologic time scale
the division of Earth history into blocks of time--eons, eras, periods, and epochs. The time scale was created using relative dating principles.
a geologic time unit; a subunit of eocs, and composed of multiple periods
4.6 billion to 544 million years ago; life developed as bacteria and softbodied, multicelled organisms. First mass extinction probably occurred near the end of the Precambrian
the central part of the Earth; containing both the inner and the outer core
thickest layer of the Earth; contains the plastic asthenosphere and a solid portion where convection currents are found
the thin and solid outermost layer of the Earth above the mantle
the solid part of the earth consisting of the crust and outer mantle
The solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows very slowly, which allows tectonic plates to move on top of it
rock formed by the solidification of molten magma
A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together
rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions