MRS. STAHL

MARINE BIOLOGY

Unit 5 & 6 Geology of the Ocean,

Water, Waves, and Tides

Some Facts

Solar system was formed more than 5 billion years ago, with Earth forming 400 million years later.

Surface was so hot that water could not remain there because there was 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%

How did the ocean form?

Hypothesis: Earth was composed of cold matter and over time energy from space and radioactive decay caused the temperatures to rise.

Process continued for several hundred million years until the core of the Earth was hot enough to melt iron and nickel.

Elements melted -> moved to the core-> raising temps to 2,000 C

Molten material moved to the surface, spread out, continued to melt and solidify, creating our landscape, separating the lighter elements from the denser ones.

They think that if there was any water present, it was stored up in the Earth’s minerals. Then, with continuous heating and cooling the water vapor was carried to the surface, it cooled, condensed, and formed the ocean!

Video

http://www.history.com/shows/how-the-earth-was-made/videos/oceans

Origin of Life Atmosphere was originally made up of gases like

carbon monoxide, carbon dioxide, methane, nitrogen, and ammonia. Oxygen is chemically active, so any other free oxygen gas present would have combined with some other element forming oxides. Therefore, oxygen did not start to accumulate in the atmosphere until the evolution of modern photosynthesis.

Oxides- Chemical compound containing at least one oxygen atom as well as another element.

Biologists also 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 (cyanobacteria), which was found in NW Australia, and is estimated to be between 3.4 and 3.5 billion years old.

The Ocean Today

The Ocean Today

139 million square miles, 362 X 10^18 gallons

362,000,000,000,000,000,000 gallons of water

Largest habitat on the planet

Referred to as the world ocean

There are four major basins, but five oceans

1.Pacific

2.Atlantic

3.Indian

4.Arctic

The area around Antarctica is referred to as the

Southern or Antarctic

Body of Water Define Examples

Sea Body of

saltwater that is smaller than an

ocean and landlocked.

Mediterranean Sea

Red Sea Caribbean Sea

Gulf 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

Label the oceans and continents

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

- Tectonic plate

- Very strong

- Weak

- Easily deformed layer of

the Earth

- Acts as a “lubricant” for

the plates to slide

Oceanic Crust Continental Crust

- Basalt

- Thin crust under the

oceans

- Thinner and denser

- More active

- Granite

- Floats on top of mantle

- Makes up the

continents

19th Century

Edward Suess

Early 1600’s

Sir Frances Bacon

1915

Alfred Wegener

1960’s H.H. Hess

Continents may have once been connected to each other.

Proposed Gondwanaland- fusion of Southern Continents (S. America, Africa, India, Antarctica, and Australia).

One supercontinent= Pangaea. Forces of the Earth’s rotation separated the continents.

Molten rock / Magma in the mantle moved by convection currents (heating and cooling of magma).

Moving Continents

Timeline of Moving Continents

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 mid-ocean ridges. On each side of the ridge, seafloor moves from the ridge towards the deep sea trenches, where it is subducted or sucked back in 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

The Forces that Drive Continental Movement

HH Hess Convection currents- the way magma moves. Magma

rises from the Earth’s core to the upper mantle, because it’s less dense than the surrounding material. When it reaches the mantle it cools, becomes denser, and sinks back into the core. The recycling causes changes in temperature called convection.

Volcanoes form when the magma breaks through the Earth’s crust.

Lines of volcanoes form underwater mountain ranges = midocean ridges

When it cools, it forms new crust = oceanic basaltic crust https://www.youtube.com/watch?v=MmMX83diwl0

Rift Valley

Where the Earth’s crust is splitting apart Narrow, steep sides, flat floor Looks like a ditch Created by tectonic activity High volcanic activity.

Tanzania’s Great Rift

Valley

Fracture Zones-

Linear regions of unusually irregular sea bottom.

Almost like cracks in the crust

SUBDUCTION ZONES

Regions where the old material sinks down into the mantle, and when it hits the magma of the mantle, it liquifies and recycles itself through convection currents back into the core.

Seafloor Spreading

Oceanic plates are diverging from one another

Magma rises along a rift zone and spreads out at the surface building new seafloor.

The age of the rocks increases as one moves away from the rift zone.

The mid-oceanic ridge is the primary site for seafloor 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

Each side is formed by a different plate and the plates scrape against each other

Divergent Boundary- plates move away from each other

Produce earthquakes and volcanoes

When they pull apart= earthquakes

Magma increases = volcano

Magnetic anomalies= proves that the ocean plates are moving.

Mid-ocean ridges are created

Mid-Atlantic Ridge (moves N. America and Europe further apart)

Convection Currents

Seafloor Spreading

Convergent Boundary- plates move together

Produce mountain chains= earthquakes

Subduction zone-> oceanic crust subducts back into the mantle

Ring of Fire

Continental crust is buoyant and less dense so one plate doesn’t easily override another.

Himalayas-> Indo-Australian Plate pushes into the Eurasian Plate (India vs. China)

Transform Fault- plates slide past each other

Earthquakes

San Andreas Fault in CA (where the N. American and Pacific plates)

Mid-ocean ridge

https://www.youtube.com/watch?v=JmC-vjQGSNM

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.

https://ocean.si.edu/ocean-videos/hydrothermal-vent-creatures

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.

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

Marianas Trench-> the deepest spot on the Earth is the Challenger Deep and is 6.85 miles deep.

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, or 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 and foraminiferans

Silicareous ooze= silica= radiolarians and diatoms

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