Transcript The Precambrian covers almost 90% of the entire history of the Earth. Chapter 22 – The Precambrian Earth Produced by S.

The Precambrian
covers almost
90% of the entire
history of the
Earth.
Chapter 22 – The Precambrian
Earth
Produced by
S. Koziol
11-26-2014
22.1 – The Early Earth
Objectives: Describe the evidence used to
determine the age of the Earth.
Understand why scientists theorize
that the early Earth was hot.
Zircon
Zircon is a stable mineral that commonly occurs
in granite.
Oldest known mineral
The oldest known mineral on Earth is zircon.
From the Jack Hills region of Australia a 4.375
billion years old ± 6 million years.
http://www.cnn.com/2014/02/24/world/oldest-earth-fragment/
Asteroid
Asteroid are metallic or silica-rich objects that
orbit the Sun between the orbits of Mars and
Jupiter.
Meteorite
Meteorite is a meteor that has fallen to and
reached the surface of Earth.
Why do scientists consider the age of meteorites when they try
to estimate the age of Earth?
Most astronomers agree that the solar system,
including Earth, formed all at once, and
therefore Earth and meteorites should be
about the same age.
Earth’s Current Estimated Age
4.54 ± 0.05 billion years
This age is based on evidence from radiometric
age dating of meteorite material and is
consistent with the ages of the oldest-known
terrestrial and lunar samples.
Why scientists theorize that the early Earth was hot.
The combined effects of radioactive decay,
asteroid and meteorite bombardment and
gravitational contraction made for a hot and
inhospitable beginning for Earth.
22.2 – Formations of the Crust and
Continents
Objectives: Explain the origin of Earth’s crust.
Describe the formation of the
Archean and Proterozoic
continents.
Earth’s earliest crust
Earth’s earliest crust likely formed as a result of
the cooling of the uppermost mantle.
Earth’s crust first formed at least
4.4 billion years ago, just 160
million years after the formation of
our solar system.
Microcontinents
Both are early Earth Continents.
Microcontinent
A microcontinent is a small
piece of continental crust
Laurentia
Laurentia was an ancient
continent that formed the
core of modern-day North
America.
Laurentia, also called the North American craton
The craton
The buried and exposed parts of a continental
shield together compose the craton, the
stable core of a continent.
Laurentia, also called the North
American craton
Laurentia
Laurentia - Ancient
continent that
contained core of
modern-day North
America
Precambrian shield
Precambrian shield is the Continental cores of
Archean and Proterozoic rock
These are the nuclear (beginning) area of Precambrian rocks present in each
of the continents.
Canadian shield
Canadian shield - The Precambrian shield in
North America.
Precambrian vs. Canadian
These are the nuclear (beginning) area of Precambrian rocks present in each of
the continents.
Precambrian
A Precambrian shield is a
continental core of Archean
and Proterozoic rock.
Canadian
Canadian Shield is the
Precambrian shield
specifically of North
America.
22.3 – Formation of the
Atmosphere and Oceans
Objectives: Describe the formation of Earth’s
atmosphere and oceans.
Identify the origin of oxygen (O2) in
the atmosphere.
Explain the evidence that oxygen
(O2) existed in the atmosphere
during the Proterozoic.
Outgassing
The process by which volcanoes vent water vapor,
carbon dioxide, nitrogen, and other substances is
called outgassing.
Cyanobacteria
are tiny, threadlike photosynthetic organisms.
Stromatolite
Stromatolite is a mat or mound composed of
billions of cyanobacteria.
Cyanobacteria
Cyanobacteria use the process of photosynthesis
to produce energy, and oxygen is given off as a
waste product.
Stromatolites
The ozone layer that filters ultraviolet radiation
originated from oxygen produced by
stromatolites.
Why was the earliest atmosphere eventually replaced
by oxygen and nitrogen gases and carbon dioxides?
Both helium and hydrogen gas have small
masses. Earth’s gravity was not great enough
to keep them from escaping into space. Gases
with higher masses like carbon and nitrogen
are unable to escape Earth’s gravity and
eventually replaced the helium and hydrogen.
Banded iron formation (BIFs)
Banded iron formation - Deposit consisting of
alternating bands of chert and iron oxide
Red bed
Red bed - Sedimentary rocks younger than 1.8
billion years that are colored by the iron
oxides in them
Banded iron
formation, Karijini
National Park, Western
Australia
Banded Iron vs. Red Bed
Banded iron (BIFs)
A banded iron formation is a
deposit that consists of
alternating bands of chert
and iron oxides.
Formed underwater and in an
oxygen-poor environment.
Red bed
A red bed is a rock younger
than 1.8 billion years that is
rusty red in color as a result
of the presence of iron
oxides.
Formed in an oxygen-rich
environment.
Red beds were formed on
land, and not under the sea
as the BIFs were.
22.4 – Early Life on Earth
Objectives: Describe the experimental
evidence of how life developed
on Earth.
Distinguish between prokaryotes
and eukaryotes.
Identify when the first
multicellular animals appeared
in geological time.
Hydrothermal vent
hydrothermal vent - Hot water vent at volcanic
seafloor rift
Amino acids
amino acids - Building blocks of proteins
During the Archean
Miller and Urey demonstrated that the basic building blocks of
life were most likely present on Earth during the Archean.
Heat, cyanide, and certain clay minerals can cause amino acids to
join together in chains.
During the Archean
Amino acids have been found in the waters of
hydrothermal vents, suggesting that proteins and nucleic
acids could have formed there during the Archean.
Does the Miller and Urey’s experiment prove that
life originated in such a liquid?
No. The experiment merely demonstrates that
some of the molecules found in living things
can arise under conditions that may be like
those of early Earth.
Single-celled organisms
Single-celled organisms that belong to the
Kingdom Monera are prokaryotes.
Prokaryote
An organism composed of a single cell that does
not contain a nucleus and is the simplest kind
of cell is a prokaryote.
Eukaryote vs. Prokaryote
They both:
have DNA as their genetic
material
membrane bound
have ribosomes
basic metabolism
amazingly diverse in forms
Prokaryote
Eukaryote
A prokaryote is a simple
organism composed of a
single cell, which does not
contain a nucleus, while
A eukaryote is an organism
that is composed of
multiple cells, which contain
nuclei and are more
complex and larger than
those of prokaryotes.
Ediacaran fauna
Ediacaran fauna are fossils of soft-bodied
Proterozoic organisms
Varangian glaciation
Varangian glaciation - Glacial event that
occurred between 700 and 800 million years
ago.
Varangian glaciation
Widespread glaciation at end of
the Proterozoic
A major extinction of acritarchs occurred near the
end of the Proterozoic, in which widespread
glaciation may have played a critical role.