Transcript Sedimentary rocks - s3.amazonaws.com

“Biological
Organization”
How living things
are organized
Core Knowledge
www.coreknowledge.org
“History of Earth & Life Forms”
In your notes, write and answer
the following question.
• Why is it important to know about the
history of the Earth, including how it was
formed?
Types of Rocks
• Review from 4th Grade
• 3 Types
– Sedimentary
– Igneous
– Metamorphic
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks8.html
Sedimentary Rocks
Sedimentary rocks made of rock fragments (sediments) or
by chemical reactions.
The classification of sediments is shown below.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks6.html
Clastic rocks–made of cemented
sediments—are classified by their grain
sizes.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks9.html
Non-clastic rocks form by chemical precipitation
(settling out from a solution.) Limestone is
made from calcite, chert from quartz, and halite
is rock salt.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks10.html
Biologic sedimentary rocks come
from the remains of organic matter.
• The most important of
these is coal.
Anthracite coal results
from the greatest
pressure and releases
the most energy when
burned. Other varieties
are bituminous and
lignite. “Petrified”
(permineralized) wood
is another organic rock.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks11.html
More about sedimentary rocks
• Shale is the most
common sedimentary
rock
• Sedimentary rocks
cover about threequarters of the land
surface
• For more about
sedimentary rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Sedrocks/Sedrocks1.html
IGNEOUS ROCKS
• Form by solidification (crystallization) of
melted minerals
Types of Igneous Rocks
• Extrusive: Lave hardens to form rocks with
tiny crystals and glassy textures.
• Intrusive: Beneath the surface, magma
hardens to form rocks with easily visible
crystal texture.
Granite
• Light-colored, coarsegrained, no pattern
• Mostly quartz,
feldspar, mica, and
hornblende
• Often used for
buildings and
monuments
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Rocks/Rocks10.html
Basalt
• Dark-colored, finegrained, extrusive
• Formed where lava
erupted onto surface
• Most widespread igneous
rocks
• Found locally in the
Palisades along west
shore of Hudson River,
Connecticut River valley
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock2.html
Gabbro
• Dark-colored, coarsegrained intrusive
• Similar composition to
basalt—plagioclase
feldspar with some
pyroxene and olivine
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock8.html
Obsidian
• Natural volcanic glass
• Forms when lava cools
very quickly
• Usually dark, but small
pieces may be clear
• Fractures along curved
(conchoidal) surface
• Used as spear and
arrow points, knives
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Slideshow/Igrocks/Igrock7.html
Pumice and other igneous rocks
• Light colored, frothy
(many air spaces)
• Same minerals as in
granite, but finer in
grain size
For more about igneous rocks:
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Igrocks/Igro
cks1.html
Metamorphic Rocks
• Formed by
heat and
pressure
changing
existing
rocks
“Foliated” rocks contain much mica and
other rocks that produce layering or banding
Gneisses and schists are common in New York City and
Westchester.
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks5.htm
l
Non-foliated metamorphic rocks include
marble, which comes from limestone, and
quartzite, which comes from sandstone
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks12.html
The Rock Cycle
Here is another version of the Rock Cycle
http://www.volcanoworld.org/vwdocs/vwlessons/lessons/Metrocks/Metrocks2.html
What is geology?
• The study of the solid Earth and the
processes by which it is shaped and
changed.
• Geology provides primary evidence for
plate tectonics, the history of life,
evolution, and past climates.
How old is the Earth?
• The age of the earth is about 4.6 billion
years, based on geologic evidence and
radioactive dating.
Geologic Time
• Geologic time: the time of the physical
formation and development of the earth
Geologic Time Periods
• EON - Longest
Two or more geological eras form an Eon, which is the largest
division of geologic time, lasting many hundreds of millions of years.
ERA
Two or more geological periods comprise an era, which is hundreds
of millions of years in duration.
PERIOD
The period is the basic unit of geological time in which a single type
of rock system is formed, lasting tens of millions of years.
AGE - Shortest
An age is a unit of geological time which is distinguished by some
feature (like an Ice Age).
Important Events of Each Era
1. Precambrian
2. Paleozoic
3. Mesozoic
4. Cenozoic
Precambrian Era
4600 to 570 MYA
• That time span previous to the
Paleozoic that comprises
approximately 90% of earth
history
• earliest forms of life, such as
bacteria and blue-green algae;
later in the period,
invertebrates such as jellyfish
Paleozoic Era
544 million to about 230 MYA
• Pangaea
• invertebrate life, such
as trilobites
• followed by amphibians,
and the beginning of
reptiles
• simple plants, such as
mosses and ferns
Pangea
• A hypothetical supercontinent that
included all the landmasses of the earth
before the Triassic Period.
Plate Tectonics
• from the Latin word tectonicus "pertaining
to building“
• is a scientific theory that describes the
large scale motions of Earth's lithosphere,
which is made of tectonic plates.
Mesozoic Era
248 to 65 MYA
• Pangaea separates into
continents
• “Age of Reptiles”;
dinosaurs
• flowering plants
• small mammals and birds
Cenozoic Era
65 MYA to the present
• Continents move into their current
positions
• Ice Age & mammoths
• Gradual development of mammals, birds
and other animals recognizable today
• Human civilization
Paleontology
• a science dealing with the life of past
geological periods as known from fossil
remains
Principle of Uniformitarianism
• the process that occurred in the past times
produced the same results as similar
processes do today
Principle of Superposition
• younger rocks are deposited on top of
older rocks
How can scientists estimate the
age of Earth?
Relative Dating
• A method of
determining the
age of a fossil by
comparing its
placement with
that of fossils in
other layers of
rock
Radioactive Dating
• Calculating the age of a substance by
analyzing the decay of radioactive
isotopes.
• In other words…scientists measure the
amount of particles that have been
released by the nucleus of an atom over
time.
Radioactive Dating
Radioactive Decay
1. Naturally-occurring radioactive materials
break down into other materials at known
rates. This is known as radioactive decay.
2. If a substance is radioactive it is unstable
and has lost or gained electrons.
3. Each radioactive isotope has its own
unique half-life. A half-life is the time it
takes for half of the parent radioactive
element to decay to a daughter product.
Elements as clocks?
• Many radioactive elements can be used as geologic
clocks. Each radioactive element decays at its own
nearly constant rate. Once this rate is known,
geologists can estimate the length of time over which
decay has been occurring by measuring the amount of
radioactive parent element and the amount of stable
daughter elements.
Radioactive Dating
• The most common form of radioactive
dating is carbon dating.
How long has there been life on
the planet?
• Using radioactive dating, scientists have
determined that life has been on planet
Earth for 2- 3 billion years!
The oldest known fossils
Stromatolites are the Earth’s oldest known fossils,
dating back to over 3 million years.
Stromatolites are fossilized layers of sedimentary
rock and blue-green algae.
Fossils
• Fossils are a record of the Earth’s history
and past life forms.
Types of Fossils
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There are four main types of fossils
1. Mold Fossils
2. Cast Fossils
3. Trace Fossils
4. True Form Fossils
Mold Fossils
• a fossilized impression made in the
substrate. A mold fossil makes a negative
image of the organism
Cast Fossils
• formed when a mold is filled in
Trace Fossils
• Trace Fossils are also called ichnofossils
• Trace fossils may be impressions made on
the substrate by an organism: for example,
burrows, borings urolites (erosion caused by
evacuation of liquid wastes), & footprints.
True Form Fossils
• True form fossils are the fossilized
remains of real animal parts or the actual
animal. These fossils can be from animals
or plants trapped in ice, tar or amber
Extinction
• The end of an organism’s existence.
• Hundreds of creatures that once lived on
the planet are now extinct, including
dinosaurs, mammoths, dodo birds, and
even modern animals, like the passenger
pigeon.
Dinosaur Extinction
• Dinosaurs became extinct about 65 million years
ago.
• There are a few theories about dino extinction,
but scientists may never know for certain.
• Theories include: asteroid impact, climate
change, volcanic eruptions, & disease carrying
insects
The Future of Geology
• Yellowstone National Park’s Supervolcano
• Yellowstone, like Hawaii, is believed to lie
on top of an area called a hotspot where
hot, molten rock rises towards the surface.
• It is not a matter of if, but when, this
supereruption will happen!