Encountering Geologic Time

Educational Application of ComputersFall II 2009 – 2010

EDUU 551Charles Pardue

What is meant by Geologic Time?

Geologic time is the interval of time occupied by the Earth's geologic history, extending from 3.9 billion years

ago (corresponding to the age of the oldest known rocks)

to the present day

It is the part of the Earth's history that is recorded in rock strata

The geologic time scale is classified in nested intervals distinguished by characteristic geologic and biologic

features

From longest to shortest duration, the intervals are:eon, era, period, and epoch

Geologic Time TermsGeologic time is grouped into the following

divisions:

Eon – The longest division of geologic time (1,000,000,000 years or more) Era – A major division of geological time consisting of two or more periods (100-300 million years) Period - A division of geological time (usually describing a system of rocks) Epoch - Subdivisions of a period and are themselves subdivided into ages (tens of millions of years) Age – Smallest division of geologic time

(millions of years)

Important Dates in Earth’s History (In millions of years)

4600 Origin of the Earth3900 Oldest Dated Crustal Rocks3800 Oldest Evidence for Life2000 First Oxygen Atmosphere/Ozone Layer Forms900 Oldest Metazoan Fossils510 Oldest Fossil Fish458 First Land Plants375 Important first step: Amphibians Evolve245 Huge Mass Extinction

(end of Permian Period & Paleozoic Era)

Important Dates in Earth’s History (In millions of years)

200 First Mammals160 First Birds145 Atlantic Ocean first opens130 Angiosperms (Flowering Plants) appear65 Adaptive Radiation of Mammals/Dinosaurs Go Extinct

(Close of the Mesozoic/Beginning of the Cenozoic Era)3.4 Age of (LUCY) Australopithecus afarensis fossils2 Pleistocene Ice Age begins.600 Age of Homo erectus fossils from Ethiopia.100 Homo sapiens appears in the fossil record.015 Last ice sheet retreats?? Your Birthday

Climbing the Geologic Time Scale

Let’s climb Mt. Everest to explore the geologic Time Scale

Mt. Everest is 29,029ft or 8,848m in height

Every 1,000m would approximate 520 million years

Every 1,000ft would approximate 160 million years

One meter would approximate 520,000 years

One foot would approximate 159,000 years

The First Mile (Hadeon Eon)

Our climb starts in the Hadeon Eon, (also known as the Rockless Eon)

4.6 to 3.9 billion years ago (0 – 4413ft/1347m/.84mi)

At this time, there is no life on earth

The crust of the Earth is solidifying into continental and oceanic plates

This Eon lasted 700 million years

The Second Mile (Archeozoic Eon)

Our second mile finds us in the Archeozoic Eon, 3.9 to 2.5 billion years ago

(4413ft/1347m/.84mi – 8826ft/2693m/1.67mi)

"Ancient Life" - The first life forms evolve - one celled organisms

Blue-green algae, archaeans, and bacteria appear in the sea

Free oxygen begins to appear into the atmosphere

This eon lasted for 1.4 billion years

Miles Three & Four (Proterozoic Eon)

13,239ft/4,040m/2.51mi (Almost halfway up!) finds us at the beginning of the Proterozoic Eon

The first multicellular life begins to appear: Colonial algae and soft-bodied invertebrates

Oxygen builds up measurably in the Mid-Proterozoic

Sponges appear in the Vendian/Ediacaran Period

(600 to 540 million years ago)

The first major extinction event occurs and all land on Earth is part of the super-continent,

Rodinia

This eon lasted for 1.96 billion years

Mile Five & Beyond (The Phanerozoic Eon)

This eon begins at 25,596ft/7,811m (4.85 miles)

This eon contains the Paleozoic, Mesozoic & Cenozoic eras

The majority of all life known to us today arose during this eon

We have 3404ft/1039m/.64mi left in our climb

This eon began 540 million years ago

The Paleozoic Era (Life explodes)

The Phanerozoic eon begins with the Paleozoic era and the Cambrian period (Age of Trilobites)

An explosion of life occurs and all existing phyla that we know today develop:

Vertebrates, mollusks, primitive fish

Toward the end of the Cambrian period, the supercontinent Rodinia breaks into smaller land masses and a mass extinction event occurs taking half of all life

on earth, probably through glaciation

The Cambrian period lasts 40 million years (252ft/77m)

It ends with us at 25,848ft/7,888m/4.9 miles with 3152ft/962m remaining

Plants, Fishes & InsectsDuring the Ordovician period the first plants & fungi

appear on land along with corals, seaweeds and gastropods in the sea

This period ends with another major extinction and finds North America under shallow seas

We are now at 26,239ft/8,007m/4.97mi and have 2,761ft/843m/.52mi left to climb

The Silurian period also gives rise to insects, jawed fishes, crinoids and vascular plants and at its end we

have2,572ft/785m/.49mi left to climb

The first amphibians occur during the Devonian period (Age of fishes) along with sharks, bony fish and coral

reefs along with another extinction that takes about 30% of all life on earth

Amphibians, Reptiles, Flight & CoalAt 26,730ft/8,157m/5.06mi with 2,270ft/693m/.43mi remaining, we find ourselves at the beginning of the

Carboniferous period

Here we find the first flying animals (winged insects) along with the first reptiles and ferns

There are also large swamps which will form the basis of the world’s coal

Amphibians and reptiles dominant the Permian period and oxygen rises close to modern levels

Another mass extinction event occurs at the end of the Permian period/Paleozoic era which takes 50% of all

animal families and 95% of all marine species

Dinosaurs & MammalsAt 27,437ft/8,373m/5.2mi, we are 1,526ft/477m/.3mi

from the top and encounter the Mesozoic era (the age of reptiles)

This era contains the Triassic, Jurassic and Cretaceous periods

Dinosaurs, crocodiles, turtles and mammals emerge during the Triassic which ends with another minor

extinction (35% of all animal families die out) and clear the way for the expansion of the dinosaurs

During the Jurassic period, the first birds and flowering plants appear along with the giant Sauropods and flying

Pterosaurs

The Cretaceous period is the heyday of the Dinosaurs, along with butterflies, bees, snakes, ants and marsupials

appearing

Mammals, Mammals, MammalsAt 28,590ft/8,725m/5.41mi, the Mesozoic era and the Cretaceous period end with the K-T extinction event which ends the reign of the dinosaurs and also takes

about 50% of all marine invertebrate species

We are 410ft/125m from the top of Mt. Everest and entering the Cenozoic era (the age of mammals)

This begins with the Tertiary period where the first large mammals appear along with primitive primates

Rodents and primitive whales make their appearance along with grasses, deer, cats, modern birds and the first apes and hominids toward the end of the Tertiary period

This period ends with us at 11ft/3m from the top of Mt. Everest

The Quaternary Period (Age of Man)

We begin this period 11ft/3m and 1.8 million years from the top of Mt. Everest

The first humans begin to evolve along with mammoths, mastodons, saber-toothed cats and giant ground sloths

Another mass extinction occurs around 10,000 years ago that removes many large mammals and birds, probably caused by the change of environment at the end of the

last ice age

This ends the Pleistocene epoch and we are .07ft/.02m from the top of Mt.

Everest

Human CivilizationWe are now almost at the summit

of Mt. Everest with .07ft/.02m remaining in our climb

In the distance remaining (13/16ths of an inch)

all human progress occurs in what is known as the Holocene epoch

Review of our climbA quick review of our climb up Mt. Everest

For the first mile of our climb, we encountered no life, with the exceptions of some blue-green algae toward the

end

Going into the second mile, we found the first primitive unicellular life and signs of free oxygen

At around 2.5 miles we found the first signs of multicellular life, more signs of free oxygen and the

Cambrian explosion of life which occurred at around 4.5 miles

Around a half mile from the top of Mt. Everest, plants, fishes and insects were found, with dinosaurs and

mammals about a quarter of a mile later

Review of our climb (cont)In the last quarter mile of our climb, the age of dinosaurs begins and ends with the age of mammals around 400ft

from the summit The age of mammals proceeds and ends about 11ft from

the top of Mt. Everest

The first ancestors of homo sapiens begin to appear at this time and the rise of civilization begins in less than

an inch from the summit

All progress as we know it takes place in this last 13/16ths of an inch of our 29,000ft climb