BSES 34 Flashcards
Earth Science (83 cards)
The largest unit of geologic unit of time
eon
Geologic time is divided into four eons
➢ the Hadean eon,
➢ the Archean eon,
➢ the Proterozoic eon,
➢ the Phanerozoic eon.
The first three eons are part of a time interval
commonly known as
Precambrian Time
a unit of geologic time that includes two or
more periods
era
After Precambrian time the ___ began
Phanerozoic eon
The first era of the Phanerozoic eon was the _____ which lasted 292 million years
paleozoic era
■ After the Paleozoic Era the ______ began and
lasted about 183 million
mesozoic era
contain fossils of a
wide variety of marine and terrestrial
life forms
Paleozoic rocks
include early forms of birds
and reptile
Mesozoic fossils
The present era is the _____, which began
65 million years ago.
Cenozoic Era
Fossils of mammals are common
in
Cenozoic rocks.
a unit of geologic time that is longer than an
epoch but shorter than an era
period
a subdivision of geologic time that is longer
than an age but shorter than a period
epoch
Epochs may be divided into smaller units of time
called
ages
are defined by the occurrence of distinct
fossils in the fossil record
ages
- Time prior to Phanerozoic Era
- Archean Eon
● 4.6-2.5 billion years ago - Proterozoic Eon
precambrian
- Large under-formed portions of
continent - Primarily Precambrian
cratons
- Craton exposed at surface
- Canadian Shield exposed by glaciation
Precambrian shield
Provide important information concerning age
of earth
origin of universe
Fragments of layer bodies that have
undergone collision and broken into pieces
origin of universe
Rocky composition
stony meteorite
Metallic composition
iron meteorite
Mixture of rocky and metallic
Proxy for core composition
Stony-iron meteorite
Organized in disks
Stars cluster in galaxies
