Geologic Time Scale Name Class Period 1 2 3 6 7 About 4.5 billion


Geologic Time Scale Name ______________________________________ Class Period 1 2 3 6 7

About 4.5 billion years ago The formation of the _ moon _____and cooling of the __ Earth ___. About 4

billion years ago

About 3.6 billion years ago 2.0 billion years ago 1.6

billion years ago

542 million to 488

million years ago

488 million to 444

million years ago

444 million to 416

million years ago

416 million to 359

million years ago

359 million to 318

million years ago

318 million to 299

million years ago Oldest rocks

The air is rich in nitrogen (N) and carbon dioxide (CO 2 ) with methane (CH 4 ), water vapor (H 2 O) and other gases, but very little _ oxygen ___is present. First cyano__ bacteria _______ Increased concentration of oxygen in the atmosphere from ___ cyanobacteria _______ metabolism Photsynthesizing organisms (cyanobacteria and plankton) thrive in shallow seas. These organisms continue to metabolize CO 2 and release __ oxygen __________ into the air as a by-product. The “Cambrian Explosion” of marine animals – many animals inhabit the shallow, calcareous-mud bottom of warm shallow oceans along the edges of the continent, including westernmost___ Connecticut ___________________.

Abundant hard-shelled _


_____ appear in the sea Calcareous - consisting of or containing calcium carbonate. Shells are made of calcium carbonate.

Bryozoans, first __ vertebrates _________________ appear Nautiloids common. __ Oxygen ______ levels in the air are at about 10


First sharks; earliest __ terrestrial _______________ animals, amphibians and wingless insects appear Huge dragonflies (50 cm wingspan!); ferns common; frogs develop. Great swamps form __ coal

____ deposits around the world.

Appalachian Mountains formed; first conifers appear; __ coal ___ deposited in eastern Ohio; first sauropsids (the group of organisms that gave rise to reptiles)

Geologic Time Scale Name ______________________________________ Class Period 1 2 3 6 7

299 million to 251

million years ago

251 million to 201.6

million years ago

201.6 million to 145.5

million years ago

145.5 million to 65.5

million years ago

Warm-blooded reptiles, forerunners of mammals, appear. Very high levels of ___ oxygen _____ (30% compared to 21% today) allow huge insects to fly despite primitive respiratory systems. _ Pangea _ forms. Mass extinction, especially of marine life, at end of Permian. Life takes tens of millions of years to recover from the Permian-Triassic extinction. More extinction marks the end of the Triassic, possibly due to _ _ meteor ___ impacts or volcanic events. This eliminates the large land reptiles and clears the way for dinosaurs to expand. Dinosaurs appear; first mammals

______ (small, rodent-like creatures)

_ Dinosaurs

____ dominate; flying reptiles appear; first known bird

65.5 million to 55.8

million years ago

55.8 million to 33.9

million years ago

33.9 million to 23

million years ago

23 million to 5.3

million years ago

5.3 million to 2.6

million years ago

2.6 million to 10

thousand years ago

Rocky Mountains began to form; first snakes; first _


grasses ____ and flowering plants appear; mass extinction of dinosaurs about 65 million years __ Himalayas ____ began to form; large radiation of mammals; earliest whales and dolphins; first bats; first large land mammals Semi-tropical plants in _ Wyoming

______ at the beginning of the Eocene

First __ apes


First _ grassland


__ Panama

______ land bridge forms


thousand years ago

10 thousand years

ago to present

Dramatic changes in climate; ice sheets cover and uncover_ Connecticut


Ice ages, mammoths, and mastodons __ Neanderthals ____existed Most recent ice age ends about 10,000 years ago. The climate rapidly warms up to its present state, and _ plants _ and _ animals ___ familiar to us today inhabit our landscape.

Geologic Time Scale Name ______________________________________ Class Period 1 2 3 6 7