Geological Eras

1. paleozoic

2. mesozoic

3. cenozoic

what are the three eras in the geological time scale (oldest first)

1. cambrian

2. ordovician

3. silurian

4. devonian

5. carboniferous

6. permian

what are the 6 periods within the paleozoic era (oldest first)

1. triassic

2. jurassic

3. cretaceous

what are the 6 periods within the mesozoic era (oldest first)

1. paleocene

2. eocene

3. oligocene

4. miocene

5. pliocene

6. pleistocene

7. recent

what are the 7 epochs within the cenozoic era (oldest first)

1. paleogene

2. neogene

3. quaternary

what are the three periods within the cenozoic era (oldest first)

archean (beginning of earth—2.5 bya)

which period is described?

• origin of life in remote past

• first fossils

• oxygen poor atmosphere

• evolution of aerobic respiration

proterozoic (2.5 bya—cambrian)

which period is described?

• earliest eukaryotes

• first fossil animals

• oxygen rich atmosphere arises

paleozoic

which period is described?

• cambrian 542 mya—permian 251 mya

mesozoic

which period is described?

• triassic 251 mya—cretaceous 65.5 mya

cenozoic

which period is described?

• paleocene 65 mya—today

devonian

what period did most life forms transition from sea to land

proterozioc

what period did eukaryotes first evolve

precambrian

what period did prokaryotes first evolve

cretaceous

what period was the extinction of the dinosaurs

pleistocene

what period was the extinction of most hominins

precambrian

what era is being described:

• formation of earth

• first life forms—prokaryotic life

• great oxygenation event—cyanobacteria began producing oxygen

paleozoic

what era is being described:

• cambrian explosion—rapid diversification of life forms

• first fish and land plants—evolution of jawless fish and the colonization of land by plants

• formation of pangaea

• permian extinction—largest mass extinction event, wiped out about 90% of species

mesozoic

what era is being described:

• age of reptiles—dominance of dinosaurs

• first birds and mammals

• cretaceous-paleogene extinction event—asteriod impact leading to extinction of dinosaurs

cenozoic

what era is being described:

• rise of mammals

• formation of modern continents

• ice age

• human evolution

hadean

what period is being described:

• formation of earth

• plant was largely molten with constant volcanic activity

archean

what period is being described:

• first stable continental crusts formed

• appearance of first prokaryotic life (including the first bacteria)

proterozoic

what period is being described:

• significant atmospheric changes (great oxygenation event)

• emergence of eukaryotic cells

• appearance of multicellular life

cambrian

what period is being described:

• cambrian explosion—rapid diversification of life with the emergence of most major animal phyla

  • early arthropods, trilobites, and first chordates appeared

ordovician

what period is being described:

• marine life thrived

• first evidence of land plants

• mass extinction at end of period likely caused by a short, intense ice age

silurian

what period is being described:

• formation of coral reefs

• first vascular plants colonized land

• jawed fish emerged

devonian

what period is being described:

• known as age of fishes

• various fish groups evolved and the first amphibians

• forests of early trees appeared

carboniferous

what period is being described:

• vast swampy forests led to significant coal deposits

• reptiles evolved from amphibians

permian

what period is being described:

• formation fo pangaea

• ended wit permian extinction

triassic

what period is being described:

• appearance of early dinosaurs and mammals

  • small and less diverse

jurassic

what period is being described:

• dinosaurs become dominant terrestrial vertebrates

• first birds appeared

• flourishing of large coniferous forests

cretaceous

what period is being described:

• emergence of flowering plants (angiosperms)

• ended with cretaceous-paleogene extinction event—caused by as astroid impact, leading to extinction of dinosaurs

paleogene

what period is being described:

• rapid diversification and growth of mammals

• first modern birds

neogene

what period is being described:

• expansion of grasslands

• emergence of modern mammal families

• first hominins in africa

quaternary

what period is being described:

• glacial and interglacial periods

• evolution of homo sapiens

paleocene

what epoch is being described:

• diversification of mammals

• appearance of small primates and early ancestors of modern mammals

eocene

what epoch is being described:

• prevalence of warm climates, allowing for lush forests

• significant evolution of mammals and birds

• emergence of early forms of modern families

• first true primates appeared

oligocene

what epoch is being described:

• cooling climate led to development of grasslands

• further diversification of mammals

• first significant appearance of apes

miocene

what epoch is being described:

• emergence of widespread grasslands and savannas

  • evolution of grazing mammals

• early hominins begin to evolve in africa

pliocene

what epoch is being described:

• continued evolution of hominins

• formation of ice sheets in the northern hemisphere

• establishment of many modern mammals

pleistocene

what epoch is being described:

• repeated glaciations (ice ages)

• megafauna like wooly mammoths and saber toothed cats roamed the earth

• development of early tools, art, and social structures by hominins

holocene

what epoch is being described:

• rise of human civilizations