Geologic Timeline

An important ingredient for fossil formation is TIME, TIME and more TIME. As a geologist it has taken many years to grasp the concept of Geologic Time with the many millions of years involved. We humans measure time within our short life spans of maybe 100 years. It still baffles me when we speak of our most fearsome and famous ancient creature T-Rex who reigned for millions of years along with his predecessors. It staggers the mind and stirs the imagination to think how the environment must have been those millions of years ago. How long could a human being survive in that alien hostile environment? Not long I believe. Besides being eaten by fierce predators, the air was very different millions of years ago. The atmosphere had ten times the amount of CO2 compared to present day. That made most of the world’s environment hot, humid and extremely uncomfortable for humans. This type of atmosphere and environment was predominant throughout the world in ancient times. During the age of dinosaurs the climate was similar throughout the world due to the concentrated landmass called Pangaea.  Continental Drift (stayed tuned to our next website) dictated the world’s landmass positions and therefore the atmospheric condition. Land mass locations, earth’s orbital spin, ocean currents, air flow and many other factors affect climates in specific parts of the world today. Dry desert, tropical forests, vast open plains as well as swamps and littoral plains exist today as it were in ancient times.  These similarities make paleo-environmental studies easier as well as comparing ancient creatures of the past to those living today. Let’s explore the Geologic Time Scale below and to help see how life on earth developed.

Geological time spiral

By United States Geological Survey - Public domain

ERA PERIOD MILLIONS OF YEARS PAST (myp) MAJOR EVENTS ASSOCIATED FOSSILS COMMENTS
CENOZOIC QUATERNARY PRESENT to 2 myp Modern Humans Hominids 2 million year old fossil found 2010 – New species found in South Africa
TERTIARY 67 to 2 myp Abundant Mammals Mammoths and Mastodons Huge mammals roam the USA, with one humped camels
MESOZOIC CRETACEOUS 140 to 67 myp Major Extinction Dinosaurs, birds and abundant Amber Mass extinction due to meteor impact and climate change
JURASSIC 208 to 140 myp Age of Birds Begin Dinosaurs, birds, ferns giant trees Abundant and diversified life on land, air and sea
TRIASSIC 250 to 208 myp Age of Dinosaurs Begin Ammonites, early Dinosaurs Dinosaurs start their rule, abundant fish and sea monsters
PALEOZOIC PERMIAN 290 to 250 myp Mass Extinction Trilobites go extinct Mass extinctions – climate change, pandemics and cosmic bombardment
PENNSYLVANIAN 365 to 290 myp Primitive Trees Appear Winged insects Also know as the CARBONIFEROUS PERIOD
MISSISSIPPIAN Amphibians are Common Coal producing era, abundant plants
DEVONIAN 405 to 365 myp Age of Fish, Earliest Amphibians, diverse land plants Fish and Shark development with great diversity Explosion of sea life
SILURIAN 430 to 405 myp First insects and fish diverse evolution Abundant Microfossils Huge insects and development of plants
ORDOVICIAN 500 to 430 myp Primitive fish appear, land plants and first sea corals take hold Age of Trilobites Explosion of Life Ancient trees and non-flowering plants are abundant and sea coral development and diversity
CAMBRIAN 570 to 500 myp Age of Trilobites – Explosion of life begins on land and sea. Trilobite fossils, eurypterids and shell fossils abundant Sea life abounds with primitive fish, trilobites, mollusks and brachiopods.
PROTEROZOIC PRE-CAMBRIAN 2,500 to 570 myp Soft bodied sea creatures appear Microfossils diversify Oxygen builds in atmosphere, algae and soft bodied creatures develop
ARCHEAN 3,800 to 2,500 myp Life Begins! Blue-green algae Stromatolites Life Appears in the seas