Transcript Unit 3 Geology - Manatee School For the Arts / Homepage

Unit 3
Geology of the Ocean,
Water, Waves, and Tides
MRS. STAHL
MARINE BIOLOGY
Some Facts
 Planet Earth began about 400 MYA
 Surface was so hot that water could not
remain there
 No free oxygen gas in the atmosphere
 Ocean began forming 4.2 billion years
ago
 Life first evolved in the ocean
 Ocean covers 70.8%
The Formation of the Oceans
1st-> Earth was composed of cold
matter and over time several
factors such as energy from
space and decay of radioactive
elements-> caused increase in
temperature.
nd
2
Heating
continued on
for several hundred
million years until the
center of the Earth was
hot enough to melt iron
and nickel.
rd
3
Elements
melted and
went to the core
(denser) and raised
the core
temperatures to
2,000 C
th
4
Molten
material
from Earth’s core
moved to the surface
and spread out,
creating some of
Earth’s landscape.
th
5
Heating
/ cooling took
place, water in the form
of water vapor was
carried to the surface
where it cooled,
condensed, and formed
the ocean.
Origin of Life
Gaseous oxygen did not start
to accumulate in the
atmosphere until the
evolution of modern
photosynthesis (3 billion
years ago).
Oxides
Chemical Compound
containing at least
one oxygen atom as
well as another
element.
The Earth was devoid of
oxygen…
Because oxygen is a
strong oxidizer of other
compounds it tends to
form oxides with these
compounds, which bind
any free oxygen.
Formed as a result of
PHOTOSYNTHESIS
Biologists theorize that the
molecules (carbon
monoxide, carbon dioxide,
nitrogen, methane, and
ammonia) formed and
accumulated in the ocean
and over time the ocean
turned into a huge, highly
concentrated bowl of
nutrient soup.
The molecules then became
organized and the first
cells evolved.
There wasn’t any oxygen
so the first cells had to be
anaerobic.
The first cells were also
heterotrophs or relied on
others for food.
The oldest marine
fossil is marine
bacteria and was
found in NW Australia
between 3.4 and 3.5
billion years old.
The Ocean Today- the largest habitat
There are Four Major Basins
1. Pacific
2.Atlantic
3.Indian
4.Arctic
What is the order from largest to
smallest?
1. Pacific
2.Atlantic
3.Indian
4.Arctic
The area around Antarctica is
referred to as the
Southern or Antarctic
Body of Water
Sea
Gulf
Define
Examples
Body of
Mediterranean
saltwater that is
Sea
smaller than an
Red Sea
ocean and
Caribbean Sea
landlocked.
Smaller body of
water that is
mostly cut off
from the larger
ocean or sea by
land formations.
Gulf of
California
Gulf of
Mexico
Persian Gulf
Continental Drift
The movement of the
seafloor caused by the
continuous movement
of the continents that
rest on it.
The seafloor is
constantly being
replaced with new
seafloor, therefore
organisms have to
adapt constantly.
Lithosphere
Asthenosphere
- Rock Sphere
- Weak
- Tectonic plate
- Easily deformed layer of
- Very strong
the Earth
- Acts as a “lubricant” for
the plates to slide
Oceanic Crust
Continental Crust
- Basalt
- Granite
- Thin crusts under the
- Floats on top of Mantle
oceans
- Thinner and denser
- More active
- Makes up the
continents
Moving Continents
Timeline of Moving Continents
Early 1600’s
Sir Frances Bacon
Proposed Gondwanaland- fusion
of Southern Continents (S.
America, Africa, India, Antarctica,
and Australia).
1915
Alfred Wegener
Molten rock / Magma in the mantle
moved by convection currents
(heating and cooling of magma).
Continents may have once been
connected to each other.
19th Century
Edward Suess
One supercontinent= Pangaea.
Forces of the Earth’s rotation
separated the continents.
1960’s
H.H. Hess
Pangaea
The man of Pangaea is
Alfred Wegener
Evidence of Continental Drift
1. Continental plates fit together like
a puzzle.
2. Distribution of Earthquakes ->
occur in narrow zones that
correspond to areas along ridges
and trenches. Most active areas of
crustal movement.
3. Temperature of Sea Bottom->
highest temps at ridges. Temps
decrease with distance from
ridges. Why do you think that
is?????
Heating magma oozing out.
4. Age of rock samples from
seafloor. Youngest rock was
found near ridges and older
rocks were found further
away.
5. Fossils collected on opposite
coasts were similar.
6. Coal deposits and other
geological formations matched
up on opposite sides of the
Atlantic.
7. Sediment gets thicker and
thicker as you move away from
the ridges.
8. Seafloor Spreading-> basalt
magma from the mantle rises to
create new ocean floor at midocean ridges. On each side of the
ridge, sea floor moves from the
ridge towards the deep sea
trenches, where it is subducted or
sucked back into and recycled back
into the mantle
9. Magnetic evidence->
* 170 reversals in the past 76 million years
(north / south polarity switched back and
forth). Reverses directions.
* Caused by fluctuations in the movement
of material in iron-nickel outer core.
* When rocks are in the molten stage they
are free to move around and act like tiny little
compasses pointing either north or south.
* When the rocks cool they keep whatever
their orientation is. There are literally stripes
on the rocks that show the magnetic bands
and they match up on either side of the mid
ocean ridge= magnetic anomalies.
Continental Drift was not accepted at
first because:
Scientists thought that
he did not have enough
evidence to prove his
theory.
 Laurasia consisted of: Europe, Asia,
and North America
 Gondwanaland- S. America, Africa,
India, Antarctica, and Australia
What did H.H. Hess propose in regards to
continental movement?
 Magma moved by convection currents
to the region below the upper mantle
and crust. The magma then would flow
laterally under the mantle (heating /
cooling took place). It would then cool
and sink backwards into the core.
Sometimes it breaks through and
volcanoes are formed-> how the mid
oceanic ridge was formed.
Cross OUT XXXXXXXXX
Page 9
The
formation of oceanic crust
and volcanoes form!!!!
We have already covered both
topics
Rift Valley
 Runs along the length of a portion of the mountain
crests. High volcanic activity.
Fracture Zoneslinear regions of unusually
irregular sea bottom.
What happens to the old ocean floor /
crust?
Regions called subduction zones
take the old material / sinks
down into the mantle and when
it hits the magma of the mantle
it liquefies and recycles itself
through convection currents
into the core.
Seafloor Spreading
 Oceanic plates are diverging from one
another, the magma rises along a rift zone
and spreads out at the surface building new
sea floor. The age of the rocks increases as
one moves away from the rift zone. The midoceanic ridge is the primary site for sea-floor
spreading. Earthquakes and volcanoes are
where seafloor spreading is occurring.
Theory of Plate Tectonics
The lithosphere is viewed as a
series of rigid plates that are
separated by earthquake belts
that are located around
trenches, ridges, and faults.
Seven Major Plates are:
 1._Pacific
 2. North American
 3. Eurasian
 4. South American
 5. African
 6. Antarctic
 7. Australian
Where plate boundaries move apart
and new lithosphere is formed
divergent plate boundaries occur.
Where the old lithosphere is
destroyed because the plates move
toward each is called convergent
plate boundaries.
Where the plates move past each
other = Faults.
Transform Fault
Special kind of fault that is
found in sections of the midocean ridge. Each side is
formed by a different plate
and the plates scrape against
each other
Rift Zones
Where the lithosphere
splits, separates, and
moves apart as new
crust is formed.
Rift Communities / Deep Sea Vents
Thriving communities of marine
organisms
Depend on chemosynthetic
activity of bacteria for their
nutrients.
Represent food webs that exist
in the absence of sunlight.
The Ocean
Bottom
Bathygraphic Features
Physical features of
the ocean bottom
The ocean bottom is
divided into two
different regions the
Continental Margin
and the Ocean Basin.
Continental Margins
 Region that lies beneath the neritic
zone.
 Consists of continental shelf and
continental slope
 Composed of granite that is covered by
sediment and have similar features to
the edge of the nearby continent.
 See Figure 3-12 on page 56 to discuss
the formation of the continental shelf.
Continental Shelf
 Generally flat areas
 40 miles wide and 430 feet deep
 Slopes gently toward the bottom of the
ocean basin
 Produced by waves that constantly
erode land mass and by natural dams,
reefs, rocks, and volcanic barriers.
Continental Slope
 Transitional level
 Shelf break is where the shelf ends and the slope




begins
Shelf break is where there is a rapid change in
depth to the seafloor
Less sediment
Submarine Canyons-> aligned with river systems
on land and they create a ripple effect on the sea
floor. At the end it fans out = Deep Sea Fan.
They are formed by turbidity currents =
underwater avalanches of sediment (large
accumulations of sediment collapse).
Continental Rise
small slope at the base of
the continental slope.
Created by landslides that
carry sediment to the
bottom of the slope.
The Ocean Basin:
Seafloor
Four Main basins: Pacific,
Atlantic, Indian, and Arctic
Composed of Basalt Rock
covered with a thick blanket of
sediment.
Outline the
rise in a
different color
in your notes.
Abyssal Plains and Hills
 Bottom of the ocean basin
 Flat
 Formed by sediment from turbidity
currents
 Spread out on the ocean floor are
abyssal hills (3300 ft. high).
 Formed by volcanic activity
Seamounts
 Steep sided formation that rises
sharply from the bottom.
 Formed by underwater volcanoes
 Some show us coral reef activity
and erosion proving that they may
have been above water at one point
in time.
Ridges and Rises
Series of large, underwater
volcanic mountains that run
through every ocean.
Separates the ocean basins
Trenches
Most common in the Pacific
Ocean
Mariana Trench-> the
deepest spot on the Earth is
the Challenger Deep and is
6.85 miles deep.
Life on the Ocean Floor
 Continental shelf is very productive because
it relatively shallow and provides lots of
sunlight and nutrients.
 Abundant marine life on the shelf
 No sunlight in the abyss.
 Limited to chemosynthetic bacteria in vent
communities
 Ocean floor organisms rely heavily on
organisms falling from above.
Composition of the Seafloor
 The entire seafloor is made up of
basalt rock with a blanket of
sediment on top.
 Sediment is made up of:
Living
organisms
land
Atmosphere
Sea
that accumulates over time
Why is the sediment so important to
organisms that live on the continental
slope, shelf, and abyssal plains?
Provides a habitat for many
organisms and a source of
nutrients for others.
Five types of sediment:
Biogenous
Hydrogenous
Terrigenous
Cosmogenous
Lithogenous
Hydrogenous
 Forms when dissolved materials come out of a
solution such as a precipitate.
 Precipitation is caused by changes in
temperature, pressure, and chemically active
fluids.
 Types include Manganese nodules (ore material
in the ocean that comes from terrigenous and
volcanic, and also hydrothermal material),
Phosphates, evaporative salts, Metal sulfides,
and carbonates (rocks with high amounts of
calcium).
Lithogenous
 Composed of fragments of Pre-existing rock
material
 Formed by Physical and Chemical Weathering> break-up of exposed rock, movement of
sediment, and large particles of rock that are
deposited near the edges of the continents and it
accumulates
 Most is made up of quartz
 Where is it found? -> Neritic zone (near shore),
beaches, continental shelves, pelagic zones
(deep sea floor).
Biogenous
 Skeletons and shells of dead marine organisms.
 Biogenous ooze= made up of 30% of
microscopic shells. When it hardens it turns
into rock and can make chalk or Diatomaceous
Earth.
 Calcareous ooze= Calcium carbonate=
Coccolithophorians (algae) and Foraminiferans
(protozoan’s)
 Silicareous ooze= Silica= Radiolarians
(Protozoan’s) and Diatoms (algae)
 Found in the Pelagic zone
Foraminiferans
Coccolithophorians
Radiolarians
Diatoms
Terrigenous
 Found in the deep sea and is formed by
accumulation of turbidites
 Turbidites are sea-bottom deposits
formed by massive slope failures where
rivers have deposited large deltas.
These slopes fail in response to
earthquake shaking or excessive
sedimentation
Turbidites
Cosmogenous
Composed of material from
outer space
Space dust and meteor debris
Forms an insignificant
amount of ocean sediment