What does geology have to do with marine biology?
A portion of the mid-Atlantic ridge above the sea surface in Iceland.
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Before we start:
Marine biology =
Geology =
Geo- , Latin for__________
The study of earth's physical structure and substance, its history, and the processes that act on it.
Ex:

 The oceans cover ____ of the planet and regulate its
___________ and ___________
 There are four ocean basins
 Pacific -
 Atlantic
 Indian
 Arctic –
 Connected to the main ocean basins are shallow seas
Ex:
Mediterranean Sea, Gulf of
Mexico, South China Sea

Fig. 2.1
 They all connect to form a world ocean where seawater, materials, and organisms can move about.
 Continuous body of water surrounding
Antarctica is the
Southern Ocean

Fig. 2.2
 Big Bang Theory
 Universe created 13.7 billion years ago.
 Earth formed 4.5 billion years ago. http://www.metaphysics-for-life.com/big-bang-theory.html

Fig. 2.2
naturenplanet.com
 In the early molten Earth, lighter materials floated toward the surface because of varying densities.
 They cooled to form the crust
 The atmosphere and oceans then formed
 Earth is the right distance from the sun for liquid water, and life, to exist

 Exists only on Earth, due to marrow temp. range required for liquid water.
 Earth is in prime position/size for liquid water
 Any closer-too hot, water evaporates
 Any further-too cold, all water freezes
 Any smaller (~30%) then not enough gravitational pull to keep water on surface, all moves to atmosphere.
 Any bigger, then too many clouds
-Importance of clouds? Greenhouse Effect
-more clouds = warmer surface (Ex: Venus)

 As Earth cooled, water vapor in atmosphere condensed, fell to surface, filled up low parts first.

Fig. 2.3

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The dense CORE is mostly iron
 Solid inner core and liquid outer core
 Believed the swirling motions produce the Earth’s magnetic field
The mantle is outside the core and under the crust
 Near molten rock slowly flows like a liquid
The crust is the outer layer, comparatively thin
 Like a skin floating on the mantle
 composition differs between oceans and continents

Continental and Oceanic Crusts
Oceanic Crust
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 Made of basalt – a dark mineral
More dense
Thinner
Younger rock; 200 mil years
Continental Crust
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 Made of granite – lighter color
Less dense
Thicker
Older rock; ~4 bil years ago

Tab. 2.2

Continental and Oceanic Crusts
 Continental crust floats higher on the mantle and ocean crust floats lower.
 That’s why ocean crust is covered by water

Fig. 2.2
 Earth today: still dynamic
 Not static and unchanging
 Continents still moving!
 Size/Shape of ocean basins defined by continental margins www3.bc.sympatico.ca
You should be asking, where is your evidence that continents move!?

 Looked at a map of
Earth, continents look like puzzle pieces.

 1 st to come up with theory about continental drift 1912.
 Suggested that all the continents had once been a supercontinent, named Pangea
 He thought, started breaking up
~180 mil years ago tower.com

 Continents as puzzle pieces, S.
America and Africa
 Other evidence:
 Similar rock formations
 Fossil records

 The Theory of Plate
Tectonics explains it all
 Continents do drift slowly around the world
 This process involves surface of the entire planet tower.com

 After WWII sonar allowed detailed maps of the sea floor
 SONAR = sound navigation ranging
 They discovered the mid-ocean ridge system!
 Chains of ridges in the middle of the oceans, like seams on a baseball
 The largest geological feature on Earth tower.com

Fig. 2.5
 Some of the mountains rise above sea level to form islands, e.g. Iceland
 The Mid-Atlantic ridge runs down the center of the
Atlantic Ocean and follows the curve of the opposing coastline
 Sonar also discovered deep trenches = deep depressions in the sea floor.

Fig. 2.6

 Rock near the ridge is young and gets older moving away from the ridge

 There is little sediment near the ridge, but it gets thicker moving away
 Sediment = loose material like sand and mud that settles on bottom of sea floor.
 Found symmetric magnetic bands parallel to the ridge where magnetic field flip-flopped

 Earth’s magnetic field, occasionally reverses direction
 Magnetic parts in molten rock, free to move.
 When cool, these particles are “frozen” and keep their orientation, even if magnetic field changes.
 Sea floor rocks have these bands, or magnetic anomalies.
 ****Sea floor NOT formed all at once****
 Offered a mechanism for movement of continents

Fig. 2.9
Cross section of the sea floor at a mid-ocean ridge.
The rocks of the sea floor show the earth’s magnetism at the time of their cooling .

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Huge pieces of oceanic crust are separating at the midocean ridges
Magma from the mantle rises through the rift (a crack) forming the ridge
The sea floor moves away from the ridge
Continuous process, called sea-floor spreading
New sea floor is created!
This explains why rocks are older and sediment is thicker as you move away from the ridge
This also explains the magnetic stripes found in the sea floor
ALL EVIDENCE for PLATE TECTONICS

 The crust and part of the upper mantle form the lithosphere
 100 km (60 mi) thick, rigid
 Broken into plates
 May be ocean crust, continent crust, or both
 The plates float on a fluid layer of the upper mantle called the asthenosphere.

•Edge of many plates, a mid-ocean ridge
• The plates move apart here, to create new sea floor
• If the plate has continental crust it carries the continent with it.
• Spread 2-18 cm/year
• Called continental drift, continents moving apart

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If seas floors are spreading, does this mean the Earth is growing bigger?
 No it means that somewhere else plates get pushed down into the mantle
 As new lithosphere is created, old lithosphere is destroyed somewhere else
Some plate boundaries are trenches where oceanic plates get “pulled down” into the mantle, melts, is recycled
This process = Subduction
Trenches are also called subduction zones
Plate boundaries are violent (if slow) collisions.

•The plates colliding can be oceanic   cont.
• Ocean plates always sink below, denser
•Produces earthquakes and volcanic mountain ranges; e.x.
Andes, Sierra Nevada oceanic   cont

oceanic   oceanic
Either plate could have dipped below the other, in this case.
•The plates colliding can be oceanic   oceanic
Earthquakes and volcanic island arcs = volcanic island chain that follow trench curvature
Ex: Aleutian Islands, Mariana Islands

continental   continental
•The plates colliding can be cont.   cont.
• Neither plate sinks, instead they buckle
•Producing huge mountain ranges
Ex: Himalayas.

Fig. 2.14
 Another type is shear boundary or transform fault
 The plates slide past each other
 Causes earthquakes
 Ex: San Andreas Fault,
CA

Fig. 2.15
Two forces move the plates:
1) Slab-Pull theory - the sinking plate pulls the rest behind it
2) Convection theory – the swirling mantle moves the plate

Continental Drift and the Changing Oceans
 200 mil years ago all the continents were joined in
Pangea
 It was surrounded by a single ocean called Panthalassa
 180 mil years ago a rift formed splitting it into two large continents
 Laurasia – North America and Eurasia
 Gondwana – South America, Africa, Antarctica, India, and Australia

Fig. 2.16
The plates are still moving today.
Atlantic Ocean is growing, Pacific is shrinking

2. The Record in the Sediments
 Studying sediments deposited in past, can learn about the history of the planet
 2 types of marine sediments:
1) Lithogenous –
2) Biogenous –
 Mostly composed of calcium carbonate or silica
 Microfossils tell what organisms lived in the past

= animal-like
Protists
= animal-like
Protists

 Past climate on Earth can be determined by:
 Chemical composition of microfossils
 Measure ratios of Mg and
Ca
 Oxygen isotope ratios
 Sr and Ca ratios in ancient coral skeletons
 Ice cores
•Fossil Agatized Coral is
Florida's state stone.
•28-25 million years ago

Fig. 2.18
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The Earth alternates between interglacial (warm) period and ice age (cold) periods
 Sea level falls during ice ages because water is trapped in glaciers on the continents
 Currently in an interglacial period
 Pleistocene Epoch , 2 mya, began last ice age…Peak was
18,000 yrs. ago

 2 main regions of the sea floor.
 1)
 2)

A. Continental Margins
= Boundaries between the continental and oceanic crusts
Consists of:
•Shelf
•Slope
•Rise

•The shallowest part
• Only 8% of the sea floor, but biologically rich and diverse
•Large submarine canyons can be found here, from past glaciation
• Ends at the shelf break , where it steeply slopes down
•Shelf 1km to 460 km (280 m) wide

•The “edge” of the continent
• Slopes down from the shelf break to the deep-sea floor
•Submarine canyons can carry sediments from the shelf to the sea floor.
•Reaches sea floor at 10,000-16,500 ft underwater
A submarine canyon

•Some, similar to a river delta = deep-sea fan

A. Continental Margins
4. Active and Passive Margins
•Active margin = the subducting plate creates a trench

A. Continental Margins
4. Active and Passive Margins
•Passive margin – no plate boundary
Ex: see next slide

Passive Margins Example: Atlantic Coast of U.S.A
•Buildup of sediments
•Broad coastal plains
•Estuaries
•Barrier Islands
•Salt Marshes

 Most of what Marine Biologists study are near continents…why do you think?

 Most of sea floor , 10,000-16,500 ft
 Abyssal plain - flat region of the sea floor, but has features:
 A
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Seamounts – submarine volcanoes
Guyots (“gee-oh”) –
 Trenches , subduction zones, = the deepest part of the ocean
 Mariana Trench is 36,163 ft deep (11,022 m) the deepest on Earth

. Mid-Ocean Ridge and Hydrothermal Vents
 At the center of the ridge, where the plates pull apart =
 Water seeps down through cracks, gets heated by the mantle
 Then emerges through hydrothermal vents
 350oC (660oF)

Fig. 2.26
 Dissolved minerals from the mantle, like sulfides, are brought up
 Black smokers form when minerals solidify around a vent
 Marine life, including chemosynthesizers, exist around hydrothermal vents

Fig. 2.27
 Chimney-like structures that build up around vents as the minerals solidify.

 Part of the Emperor Seamount chain
 Made from a Hotspot =
 Pacific plate, slowly moving over the stationary hotspot
 Much debate still, a stationary hotspot or various cracks in the crust.
 http://www.youtube.com/watch?v=hOCfb9ox_90

Page 36

 In S.Atlantic, following the Mid-Atlantic Ridge between the remote islands of St. Helena and Ascension.
 <iframe width="560" height="315" src="http://www.youtube.com/embed/5MC23C5HXUg" frameborder="0" allowfullscreen></iframe>
 http://www.youtube.com/watch?v=5MC23C5HXUg

Tab. 2.1
 Helpful table for studying

 What does geology have to do with marine biology?
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Profoundly influences habitats= The natural environment where organisms live
Sculpts shorelines
Determines water depth
Controls if muddy, sandy, rocky bottom
Creates new islands, ridges, mountains for organisms to colonize