key words Flashcards
what are meteorites
a piece of rock or metal that has fallen to the earth’s surface from outer space as a meteor. Over 90 per cent of meteorites are of rock while the remainder consist wholly or partly of iron and nickel.
aggregation
the formation of a number of things into a cluster.
hydrosphere
all the waters on the earth’s surface, such as lakes and seas, and sometimes including water over the earth’s surface, such as clouds.
geodynamo
The mechanism by which the earth’s magnetic field is generated, believed to resemble a self-exciting dynamo and to involve circulatory and convective motions and electrical currents within the earth’s liquid outer core
fossils
traces of organisms preserved in the geologic record
what are mass extinctions
The extinction of a large number of species within a relatively short period of geological time, thought to be due to factors such as a catastrophic global event or widespread environmental change that occurs too rapidly for most species to adapt.
precambrian
before the cambrian explosion
hadean eon
earliest eon 4.56 billion years ago to 3.9 billion years ago
archean eon
second eon, crust formed 3.9 - 2.5 billion years ago
proterozoic eon
3rd eon last part of precambrian 2.5 billion - 542 milllion years ago
phanerozoic eon
cambrian explosion 542 million years ago to today
nebula hypothesis
origin of world is rotating cloud of gases and fine dust
planetesimals
small km sized chunks made of compacted gas and dust
differentition
the earth was all liquid so different counterparts could move (heaviest to the centre) leaving a planet with layers: crust mantle and core
earths core
inner one is solid, outer is liquid
