Download 3rd Rock Notes 2013

Third Rock From the Sun Notes
Geologic Time
Eras
Precambrian – the oldest and largest
division of geologic time (87% of Earth’s
history)
 Time Frame – 4600 to 544 million
years ago
Organisms
oldest
–
definite fossils known
prokaryotes
(lacking a cell membrane)
Similar
to cyanobacteria; (oxygenproducing & underwent photosynthesis)
It
was 2 billion years later before the
origin of eukaryotes
By
the end of this era we had the origin of
shell-less invertebrates
Paleozoic
Time Frame – 544 to 245 million years ago
 Periods – (from oldest) Cambrian,
Ordovician, Silurian, Devonian,
Carboniferous, Permian

Organisms
– (referred to as the explosion of life)
At
the beginning was the origin of most
invertebrates
 Then
the first vertebrates & first land plants
appeared
Around
the middle of this era the first
amphibians and insects appeared
During
the second half of this era the first
reptiles appeared.
Mesozoic
Time Frame – 245 to 66 million years ago
 Periods – Triassic, Jurassic, and Cretaceous
 Organisms –
◦ During Triassic the first mammals &
dinosaurs appeared
◦ Jurassic-dinosaurs become dominant
◦ Cretaceous- mammals began to spread
out and flowering plants appeared & the
dinosaurs became extinct

Cenozoic
 Time
Frame – 66 million years ago to
the present. Mammals flourished.
 Periods –
◦ Tertiary – Paleocene, Iocene, Oligocene,
Miocene, Pilocene
◦ Quaternary – Pleistocene, Recent
The Geologic
Time Scale
Based on
*Fossils
*Correlation
Later
*Calibrated with
radiometric
dating
Evidence - fossils
 Relative
Dating – The age of a fossil
in terms of other fossils around it.
Fossils in layers of sedimentary rocks,
younger are on top & older are in the
lower layers.
◦ Index Fossils – are used to coordinate
the fossils at one location with those at
another. For ex. One island with another
Evidence Cont.
 Absolute
Dating – age is given
in years instead of relative terms
◦ Ex. Radioactive Dating – determines
the age of fossils by looking at the
isotopes of elements that
accumulate with the organisms
when they were alive
◦ Confirmed the Geologic Time Scale
Newest Technology
Radiometric Calibration
 - uses half life of elements for date
estimations.
 -computer simulations and sampling is the
newest method for fossil estimations

Imperfection of the Fossil Record
 Organisms
had to die on the right
place and right time for burial
conditions to favor fossilization
 Rock must be exposed for us to see
 The fossil record is incomplete
because of this.
Fossils
Description
 Fossils
are mineralized or petrified
replicas of skeletons, bones, teeth,
shells, leaves and seeds or
impressions of such items; usually
found in sedimentary rock.
Types
 Remainders
– the actual body or
parts of an organism
 Petrified
– the bone has been
replaced by mineral
 Molds/Casts
–
◦ Molds – bone gets buried and the
sediment turns into rock, and the animal
is dissolved away
◦ Casts – if another mineral fills the mold
and hardens in the shape of the old
animal it becomes a cast
Carbonization
– if an animal dies
and the sediment crushes the animals
as fossilization is occurring, you will
have a thin black coating on the fossil.
Much of this is coal.

Impression – (trace fossil) there is an
impression of the fossil, but the fossil is gone

Amber – resin from certain trees that small
insects and other organisms get trapped in

Tracks – footprints left in the sediment that
solidifies
◦ Ex. dinosaur tracks in Texas
 Burrows
– an animal like a worm
burrows into the mud, then the
burrow becomes fossilized
 Coprolites
– fossil excrement can
sometimes give definitive knowledge
about the eating habits of the animals
 Gastroliths
– smooth, polished
stones that are found in the abdominal
cavities of the skeletons of dinosaurs.
They are thought to have helped the
huge animals grind up vegetation in
their stomachs.
Fossil Record
 Ideal
Conditions – quick burial and the
presence of some hard parts
 Meaning – tells us the date of the organism
by dating the rock. You can tell what came
before what by superposition; mass
extinctions; pop. explosions.
 Support for Evolution – changes over time
can be seen
Examples of Fossil Record

Burgess Shale – Middle Cambrian Period
(505 mya)
◦ Exceptional preservation of soft parts

Jurrasic Solnhofen Limestone (200-245
mya)
Description
 Plate
tectonics is the theory
explaining the movement of the
plates and the processes that
occur at their boundaries.
GEOLOGIC PROCESSES


The earth is made up of a core, mantle, and crust
and is constantly changing as a result of processes
taking place on and below its surface.
The earth’s interior consists of:
◦ Core: innermost zone with solid inner core and
molten outer core that is extremely hot.
◦ Mantle: solid rock with a rigid outer part
(asthenosphere) that is melted pliable rock.
◦ Crust: Outermost zone which underlies the
continents.
GEOLOGIC PROCESSES

Major features of the earth’s crust and upper
mantle.
Figure 15-2
Volcanoes
Abyssal hills
Oceanic crust
(lithosphere)
Abyssal Oceanic
floor
ridge
Abyssal
floor
Trench
Folded
mountain
belt
Abyssal plain
Craton
Continental
shelf
Continental
slope
Continental
rise
Continental crust (lithosphere)
Mantle (lithosphere)
Fig. 15-2, p. 336
Spreading
center
Collision between
two continents
Subduction
zone
Continental
crust
Oceanic
crust
Ocean
trench
Oceanic
crust
Continental
crust
Material cools Cold dense
as it reaches material falls
the outer back through
mantle
mantle
Hot
Mantle
material
convection
rising
cell
through
the
mantle
Two plates move
towards each other.
One is subducted
back into the mantle
on a falling convection
current.
Mantle
Hot outer
core Inner
core
Fig. 15-3, p. 337
GEOLOGIC PROCESSES

Huge volumes of heated and molten rack
moving around the earth’s interior form
massive solid plates that move extremely
slowly across the earth’s surface.
◦ Tectonic plates: huge rigid plates that are
moved with convection cells or currents by
floating on magma or molten rock.
The Earth’s Major Tectonic Plates
Figure 15-4
Continental Drift

Wegener proposed
the theory that the
crustal plates are
moving over the
mantle.

Supported by:

Fossil, rock type
evidence and
coastline shapes.
Earth ~200 million years ago
The Continental Drift Hypothesis
Proposed by Alfred Wegener in 1915.
Supercontinent Pangaea started to break up about 200
million years ago.
Continents "drifted" to their present positions.
Pangea is now known to be the latest in a succession
of “super continents”
Continental Drift: Evidence
Geographic fit of South America and Africa
Fossils match across oceans
Rock types and structures match across
oceans
Continental
Drift:
Evidence
Tight fit of
the continents,
especially
using
continental
shelves.
Continental Drift:
Evidence
Fossil critters and plants
Continental
Drift:
Evidence
Correlation of
mountains
with nearly
identical
rocks and
structures
Continental
Drift:
Evidence
Glacial features
of the same age
restore to a
tight polar
distribution.
Continental Drift – current
movement

While not every plate moves at the same
speed, or even moves at all relative to
every other plate, an overall average
velocity of speed for present-day plates is
about 2.5 cm per year.
The Earth’s Major Tectonic Plates

The extremely slow movements of these
plates cause them to grind into one another at
convergent plate boundaries, move apart at
divergent plate boundaries and slide past at
transform plate boundaries.
Figure 15-4
Fig. 15-4, p. 338
JUAN DE
FUCA PLATE
EURASIAN PLATE
NORTH
AMERICAN
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
ARABIAN
AFRICAN PLATE
PLATE
PACIFIC
PLATE
SOUTH
AMERICAN
NAZCA PLATE
PLATE
SOMALIAN
SUBPLATE
CHINA
SUBPLATE
PHILIPPINE
PLATE
INDIAAUSTRALIAN
PLATE
ANTARCTIC PLATE
Divergent plate
boundaries
Convergent plate
boundaries
Transform
faults
Fig. 15-4a, p. 338
The Theory of Plate Tectonics
Earth’s outer shell is broken into thin, curved plates
that move laterally atop a weaker underlying layer.
Most earthquakes and volcanic eruptions happen at
plate boundaries.
Three types of relative motions between plates:
Why do the plates move?
Two related ideas are widely accepted:
Slab pull: Denser, colder plate sinks at subduction
zone, pulls rest of plate behind it.
Mantle convection: Hotter mantle material rises
beneath divergent boundaries, forces the cooler
material to sink at subduction zones.
So: moving plates, EQs, & volcanic eruptions are due
to Earth’s loss of internal heat.
Convection Currents
The force responsible for plate movement is __________.
 Oceanic
Crust is more dense than
Continental Crust.
 Continental Crust is thicker than Oceanic
Crust.
 Because of this the continental crust
floats on top of the oceanic crust.
 Plates
move apart from each other at
divergent boundries.
 Molten rock flows up the resulting cracks
forming oceanic ridges.
 Internal
forces push two plates together.
 Continental-Continental
◦ The light crusts colliding causes them to push up
and form high mountain ranges like the Himalayas.
 Continental-Oceanic
◦ Oceanic is denser and dives under lighter
continental. This causes trenches when the oceanic
dives and mountain ranges when the continental
buckles and folds.
 Oceanic-Oceanic
◦ Collision of 2 dense plates causes deep trenches
because they are each trying to dive under the
 Plates
slide past each other often causing
earthquakes.
◦ Ex. San Andreas Fault (California)
Trench
Volcanic island arc
Craton
Transform
fault
Lithosphere
Asthenosphere
Divergent plate boundaries
Lithosphere
Rising
magma
Asthenosphere
Convergent plate boundaries
Lithosphere
Asthenosphere
Transform faults
Fig. 15-4b, p. 338
Plate Boundaries
apart
Boundary – moving _____
together
 Convergent Boundary – moving ________
 Transform Fault Boundary – moving
sideways past each other
________________________
 Divergent
Divergent boundaries: Chiefly at oceanic ridges
(aka spreading centers)
Boundaries
 Divergent – the plates move
apart in opposite directions.
Divergent boundary of two continental plates.
rift
valley
East African Rift
Creates a __________. Example: _____________
Divergent
boundaries
also can rip
apart (“rift”)
continents
Presumably,
Pangea was
ripped apart by
such continental
rifting & drifting.
Convergent
– the plates push
together by internal forces. At most
convergent plate boundaries, the
oceanic lithosphere is carried
downward under the island or
continent. Earthquakes are common
here. It also forms an ocean ridge
or a mountain range.
Convergent boundary of two oceanic plates.
island arc and a _____.
trench Example: _____
Japan
Creates an ________
Subduction zones form at convergent boundaries
if at least one side has oceanic (denser) material.
Modern examples: Andes, Cascades
Major features: trench, biggest
EQs, explosive volcanoes
Another subduction zone—this one with
oceanic material on both sides.
Modern example: Japan
Boundaries (Continued)
 Transform – plates
slide next or past
each other in
opposite directions
along a fracture.
 California will not fall
into the ocean!
Pacific Plate
The Pacific plate is off the coast of
California. Lots of volcanoes and
earthquakes occur here.
 “California will fall into the ocean” idea.
 It is the largest plate and the location of
the ring of fire.

GEOLOGIC PROCESSES

The San
Andreas Fault
is an example
of a transform
fault.
Figure 15-5
Most transform
boundaries
are in the oceans.
Some, like the one
in California, cut
continents.
The PAC-NA plate
boundary is MUCH
more complex than
this diagram shows.
Transform-fault boundary where the North American
past each other.
and Pacific plates are moving ____
San Andreas Fault in California
Example: ________________
Importance
 Plate
movement adds new land at
boundaries, produces mountains,
trenches, earthquakes and
volcanoes.
Hotspots, such as the one under Hawaii,
have validated plate tectonic theory.
Plate Boundaries Review





divergent
Places where plates move apart are called _____________
boundaries.
rift valley
When continental plates diverge a ___________
is
formed.
When two oceanic plates converge what is created?
an island arc and a trench
_________________
The Appalachians formed mainly from continental plate
folded
collisions and therefore are a __________
mountain
range.
Convection currents.
The force moving the plates is ____________
The Rock Cycle – the interaction
of processes that change rocks
from one type to another
Rock Cycle
Figure 15-8
Erosion
Transportation
Weathering
Deposition
Igneous rock
Granite,
pumice,
basalt
Sedimentary
rock
Sandstone,
limestone
Heat, pressure
Cooling
Heat, pressure,
stress
Magma
(molten rock)
Melting
Metamorphic rock
Slate, marble,
gneiss, quartzite
Fig. 15-8, p. 343
Steps
Oxygen

The most abundant element in Earth’s
crust.
Nitrogen

The most abundant element in the Earth’s
atmosphere.
Iron

The most abundant element in the Earth’s
core.
Aluminum

The element commercially extracted
from bauxite
Relationships Between All Three
Rocks
 All
three rocks are being
recycled and converted to all
of the classes
Rock Classification
Igneous

Description – forms the bulk of the earth’s
crust. It is the main source of many non-fuel
mineral resources.
 Classification
–
◦ Intrusive Igneous Rocks – formed from
the solidification of magma below ground
◦ Extrusive Igneous Rocks – formed from
the solidification of lava above ground
Igneous (Continued)
 Examples
– Granite, Pumice,
Basalt, Kimberlite (Diamond,
Tourmaline, Garnet, Ruby,
Sapphire)
Sedimentary
 Description
– rock formed from
sediments. Most form when rocks
are weathered and eroded into small
pieces, transported, and deposited in
a body of surface water.
Clastic
– pieces that are
cemented together by quartz and
calcium carbonate (Calcite).
Examples: sandstone (sand stuck
together), Conglomerate (rounded
& concrete-looking) and Breccia
(like conglomerate but w/ angular
pieces)
Sedimentary (Continued)
 Nonclastic
–
◦ Chemical Precipitates – limestone
precipitates out and oozes to the
bottom of the ocean (this is why there is
a lot of limestone in S.A.)
◦ Biochemical Sediments – like peat & coal
◦ Petrified wood & opalized wood
Metamorphic
Description – when preexisting rock is
subjected to high temperatures (which
may cause it to partially melt), high
pressures, chemically active fluids, or a
combination of these
 Location – deep within the earth

Examples:

Contact Metamorphism- rock that is next
to a body of magma
Ex. limestone under heat becomes marble
through crystallization

Limestone -> marble
sandstone -> quartzite
shale -> hornfelds (slate)

Dynamic Metamorphism – earth
movement crushes & breaks rocks along
a fault. Rocks may be brittle- (rock and
mineral grains are broken and crushed)
or it may be ductile- (plastic behavior
occurs.)

Rocks formed along fault zones are
called mylonites.
Metamorphic (Continued)
◦ Regional Metamorphism – during
mountain building; great quantities of
rock are subject to intense stresses and
heat
 Ex. cont. shelves ram together
Progressive
Metamorphism – One
form of rock changing into another
shale->slate->schist->gneiss
coal->graphite
granite->gneiss