Geologic Ages
Overview
Topics covered in this section:
Introduction
In this section we present a global overview of the standard geologic
ages. These ages apply to the entire planet, not to Romania specifically.
However, they do provide a context in which we can talk about
prehistoric Romania later.
Since the geologic ages are not our primary historic focus, however,
we will be very brief in our overview ... just enough to give you a taste
of what's happening in each era.
Precambrian Era
The Precambrian Era takes us all the way back to the very beginning of
our planet.
Hadean Time
Hadean Time covers the birth of our planet, more than 4 billion years
ago. There is no geologic record this old.
Archean Eon
During the Archean Eon, between 4 billion and 2.5 billion years ago,
the planet's continents, atmosphere, and ocean form. Of course, the
continents were not in the same positions that they're in now. The
beginnings of life appear in the form of one-celled organisms known
as prokaryotes. These are the distant ancestors of present-day bacteria
and cyanobacteria.
Proterozoic Eon
Some 2.5 billion to 570 million years ago, the atmospheric oxygen
increases, allowing more complex forms of life to evolve. Organisms,
known as eukaryotes, possess a cellular nucleus and nuclear membrane.
Multi-cellular organisms make their appearance.
Paleozoic Era
Life on the planet is almost extinguished during the Paleozoic Era.
In the beginning we see a tremendous spurt of growth. Then near the end,
nearly every life form is wiped out.
Cambrian Period
Between 570 million and 500 million years ago, during the Cambrian
Period, there is an explosion of multicellular life.
Ordovician Period
During the Ordovician Period, some 500 million to 435 million years
ago, ocean vertebrates and primitive life on land appear.
Silurian Period
In the Silurian Period, 435 million to 410 million years ago, the
first insects appear on a land that sees its first plants.
Devonian Period
The Devonian Period, 410 million to 360 million years ago, is marked
by the appearance of creepy crawlers like spiders and mites. Amphibians
also make their debut.
Carboniferous Period
Coal begins to form 360 million to 290 million years ago, giving the
name Carboniferous Period to this timeframe. The first true reptiles
appear.
Permian Period
The Permian Period, 290 million to 250 million years ago, is a
deadly period. Some 90 percent of all organisms die out as they fall
prey to a mysterious mass extinction. Nearly all life forms
are wiped out! Reptiles survive, however, and inherit the earth.
Mesozoic Era
The long era of dinosaurs begins.
Triassic Period
During the Triassic Period, 240 million to 205 million years ago,
small dinosaurs, ichthyosaurs, and plesiosaurs appear. We also see the
appearance of the first true mammals.
Jurassic Period
This is the period made popular by Hollywood movies. The Jurassic
Period, 205 million to 138 million years ago, heralds the appearance
of huge dinosaurs and flying pterosaurs. It's a time when we see the
emergence of the oldest known birds. And, of course, that Hollywood
favorite, Tyrannosaurus Rex snaps its huge jaws around less fortunate
prey.
Cretaceous Period
Again the planet faces near extinction of all life forms, this time
during the Cretaceous Period, 138 million to 65 million years ago.
Following a period of global warming, which encourages the spread of
the dinosaurs' domain, a sudden mass extinction, perhaps due to an
asteroid impact, spells doom for the dinosaurs. Some 70 percent of all
organisms are wiped out.
Cenozoic Era
We now enter a kinder, more gentle, era. Sort of, at least.
Tertiary Period
Mammals begin to claim their territory.
Paleocene Epoch
During the Paleocene Epoch, 65 million to 55 million years ago,
mammals inherit the earth. Chief among the early mammals are marsupials,
lemuroids, insectivores, primitive hoofed animals, and creodonts (the
carnivorous ancestors of all cats and dogs).
Eocene Epoch
A number of mammals appear simultaneously in Europe and North America
during the Eocene Epoch, 55 million to 38 million years ago. Ancestral
forms of the horse, rhinoceros, and camel appear. Modern groups such as
primates, bats, and squirrel-like rodents appear. Mammals begin to
adapt to marine life.
Oligocene Epoch
During the Oligocene Epoch, 38 million to 24 million years ago, the
rhino ranks as the largest land mammal of any age. Also making their
debut are elephants, cats and dogs, monkeys, and great apes.
Miocene Epoch
In the Miocene Epoch, 24 million to 5 million years ago, the global
climate cools, fostering the establishment of the Antartic ice sheet.
Raccoons and weasels make their initial debut. Large apes roam across
Africa and southern Europe.
Pliocene Epoch
During the Pliocene Epoch, 5 million to 1.6 million years ago, the
climate becomes cooler and drier. Mammals are well-established as the
dominant terrestrial life form. The rapid evolution of one group of
mammals, the primates, produces species considered the direct ancestors
of modern humans.
Quaternary Period
The Quaternary Period is a period of continual advances and declines
of Ice Ages, followed by the present day.
Pleistocene Epoch
The Pleistocene Epoch extends from 1.6 million years ago to the
most recent Ice Age of 10,000 years ago. Glacier ice spreads over
more than one-fourth of the Earth's land surface, drastically dropping
the ocean levels. Modern humans make their debut and begin their
migrations.
Holocene Epoch
We are currently in the Holocene Epoch, which begins 10,000 years
ago and extends to the present. The global climate moderates as the
last of the continental ice sheets rapidly retreat from Europe and
North America. Sea levels rise. All of recorded human history occurs
during the Holocene Epoch.
Go Elsewhere
At this point, you have a couple of options:
Enjoy your stay and have a great day!
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