Dying out

Longest unit of geologic time

Subdivision of an eon

Dying out of many species on Earth within a short period of time

Subdivision of an era

Stretch of land that connect two continents that were previously separated by water

Separation of a population of organisms from the rest of its species due to a physical barrier

Subdivision of a period

Changes in species overtime as they adapt to the environment

Time line of Earth's past

Sudden evolution of new, complex life forms

Youngest era of the Phanerozoic eon

Body of water formed when ocean water floods continents

Oldest era of the Phanerozoic eon

Ancient landmass that separated into present-day continents

Middle era of the Phanerozoic eon

Oxygen-poor environment where, over time, plant material changes into coal

Changed from liquid to gas

Mesozoic marine reptile with a small head, long neck, and flippers

Dominant Mesozoic vertebrate that walked with legs positioned directly below its hips

Mesozoic flying reptile with large, bat-like wings

Most recent epoch, which began around 12,000 years ago

Gouge made by rocks carried in glaciers

Time when much of Earth's surface is covered by glaciers

Large mammal of the Cenozoic era

First epoch of the Quaternary Period

To make an assumption about something that is not positively known

Earliest part of Earth's history set before the current Phanerozoic Eon -- encompasses 90% of Earth's history