1. What does geology have to do with marine biology?
A portion of the mid-Atlantic ridge above the
sea surface in Iceland.
Chapter 2
The Sea Floor
What does geology have to do with marine biology?
Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

2. 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:

3. The Water Planet The Geography of the Ocean Basins
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:

4. The Geography of the Ocean Basins
Fig. 2.1
The Geography of the Ocean Basins
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

5. The Structure of Earth Big Bang Theory Fig. 2.2

6. Fig. 2.2
The Structure of Earth
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
naturenplanet.com

7. Water
Exists only on Earth, due to narrow 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)

8. How did the water form?
As Earth cooled, water vapor in atmosphere condensed, fell to surface, filled up low parts first.

9. Fig. 2.3

10. The Structure of Earth Internal Structure
The dense CORE is mostly ___________.
Solid inner core and liquid outer core
Believed the swirling motions in outer core produce Earth’s magnetic field
The _____________ 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

11. The Structure of Earth Continental and Oceanic Crusts
Continental Crust
Made of basalt – a dark mineral
Younger rock; < 200 mil years M
Thicker
Older rock; ~4 bill years ago

12. Tab. 2.2

13. The Structure of Earth 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

14. The Origin and Structure of the Ocean Basins
Fig. 2.2
The Origin and Structure of the Ocean Basins
Earth today: still dynamic
Not static and unchanging
Continents still moving!
Size/Shape of ocean basins defined by continental margins
www3.bc.sympatico.ca

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

16. Alfred Wegener
1st to come up with hypothesis of continental drift 1912.
Suggested that all the continents had once been a supercontinent, named ______________.
He thought, broke up.
-today: ~180 mil years ago
Not widely accepted, he could not explain HOW the continents moved. More evidence accumulated…scientists concluded that continents did drift, as part of plate tectonics—whole surface of earth.
tower.com

17. The Theory of Plate Tectonics
More evidence led to…Theory of Plate Tectonics.
Explains the How
Continents do drift slowly around the world
Process involves surface of the entire planet
tower.com

18. The Theory of Plate Tectonics Discovery of Mid-Ocean Ridge
After WWII sonar allowed detailed maps of the sea floor
SONAR =
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

19. Mid-Ocean Ridge System
Fig. 2.5
Mid-Ocean Ridge System
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 depressions in the sea floor.

20. Fig. 2.6

21. Significance of the Mid-Ocean Ridge
Rock near the ridge is young and gets older moving away from the ridge

22. Significance of the Mid-Ocean Ridge
________________ = loose material like sand and mud that settles on bottom of sea floor.
Little sediment near ridge, gets thicker moving away
Found symmetric magnetic bands parallel to the ridge which alternate normal and reversed magnetisms

23. More Evidence: Magnetic Anomalies
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.

24. Creation of Sea Floor
Huge pieces of oceanic crust are separating at the mid-ocean ridges
Create cracks = rifts
Magma from the mantle rises through the rift forming the ridge
The sea floor moves away from the ridge
This continuous process is 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

25. Cross section of the sea floor at a mid-ocean ridge.
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.

26. Sea-Floor Spreading and Plate Tectonics
The crust and part of the uppermost part of mantle form the ______________________.
100 km (60 mi) thick, rigid
Broken into ______________.
May be ocean crust, continent crust, or both
The plates float on a fluid layer of the upper mantle called the ________________________.
Sea floor spreading ½ of story, Lithospheric plates the other half

27. 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

28. Plate Boundaries at Trenches
As new lithosphere is created, old lithosphere destroyed somewhere else
Some plate boundaries are trenches where one plate sinks below the other, into the mantle and melts
This process =__________________
______________are also called _______________zones
Otherwise earth would be expanding and we know its not.
We learned some plate boundaries were at ocean ridges, others at these subduction zones

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

30. The plates colliding can be 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:

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

32. Shear boundary Another type: shear boundary or transform fault
Fig. 2.14
Shear boundary
Another type: shear boundary or transform fault
The plates slide past each other
Causes earthquakes
Ex:

33. Two forces move the plates: 1) Slab-Pull theory –
Fig. 2.15
Two forces move the plates:
1) Slab-Pull theory –
2) Convection theory –

34. Geological History of the Earth 1
Geological History of the Earth 1. 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 ______________________.
180 mil years ago a rift formed splitting it into two large continents
______________– North America and Eurasia
______________– South America, Africa, Antarctica, India, and Australia

35. The plates are still moving today.
Fig. 2.16
The plates are still moving today.
Atlantic __________
Pacific ___________

36. Geological History of the Earth The Record in the Sediments
Studying sediments deposited in past, can learn about the history of the planet
Two types of marine sediments:
1) Lithogenous – from the weathering of rock on land
2) Biogenous – from skeletons and shells of marine organisms
Mostly composed of calcium carbonate or silica
Microfossils tell what organisms lived in the past

37. Radiolarians: animal-like Protists
Foramaniferans: animal-like Protists

38. Oceans and Climate in the Past
Past climate on Earth can be determined by:
Chemical composition of microfossils
Measure ratios of Mg to 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

39. Geological History of the Earth Climate and Changes in Sea Level
Fig. 2.18
Geological History of the Earth Climate and Changes in Sea Level
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
The climate of the Earth fluctuates rythmically through much of its history.

40. The Geological Provinces of the Ocean
2 main regions of the sea floor
Continental Margins =
-submerged edge of the continents.
-boundaries between continental and oceanic crust
Deep-sea floor

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

42. Continental Margins 1. Continental Shelf
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 .6mi to 470 mi
wide

43. Continental Margins 2. Continental Slope
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

44. Continental Margins 3. Continental Rise
Consists of sediment building up on the sea floor at the base of
the slope
Some, similar to a river delta = deep-sea fan

45. Continental Margins 4. Active and Passive Margins
Active margin = the subducting plate creates a trench
Earthquakes and volcanoes
Ex:
Narrow shelf
steep slope
little or no rise
Steep, rocky shorelines
The biological habitats depends on the plate tectonic activity happening along the continental margins of

46. Continental Margins 4. Active and Passive Margins
Passive margin – no plate boundary
Wide shelf
gradual slope
thick rise
Ex: see next slide
The biological habitats depends on the plate tectonic activity happening along the continental margins of

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

48. Deep-Ocean Basins Most of sea floor , 10,000-16,500 ft
Abyssal plain = the deep sea floor, relatively flat, but has features:
Abyssal hills, submarine channels, rises, plateaus
Seamounts – submarine volcanoes
Guyots (“gee-oh”) – flat-topped seamounts
Trenches , subduction zones, = the deepest part of the ocean
Mariana Trench is 36,070 ft deep (10,994 m) the deepest on Earth

49. Mid-Ocean Ridge and Hydrothermal Vents
At the center of the ridge, where the plates pull apart a depression = central rift valley
Water seeps down through cracks, gets heated by the mantle
Then emerges through hydrothermal vents, deep sea hot springs.
warm, 68F
Some hot, 660F

50. C. Mid-Ocean Ridge and Hydrothermal Vents
Fig. 2.26
C. Mid-Ocean Ridge and Hydrothermal Vents
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

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

52. Hawaiian Islands Part of the Emperor Seamount chain
Made from a Hotspot = a place where a plume of magma rises deep in the mantle and erupts.
Pacific plate, slowly moving over the stationary hotspot
Much debate still, a stationary hotspot or various cracks in the crust.

53. Page 36

54. Geology and Marine Biology
What does geology have to do with marine biology?
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