Marine 11 4-11

Under the Sea!! Under the Sea!!

The creation and destruction of the sea floor

The creation and destruction of the sea floor

Constant state of changeConstant state of change

Constant creation and destruction through SEAFLOOR SPREADING

New crust emerges from rift valley in MID OCEAN RIDGE

Old floor sinks in the TRENCHES

Whole cycle takes 185 to 200 million years Same rate at which your

fingernails grow!

Constant creation and destruction through SEAFLOOR SPREADING

New crust emerges from rift valley in MID OCEAN RIDGE

Old floor sinks in the TRENCHES

Whole cycle takes 185 to 200 million years Same rate at which your

fingernails grow!

Seafloor spreadingSeafloor spreading

Four types of evidence for sea floor spreading

Four types of evidence for sea floor spreading

Radiometric dating

Sediment samples Rheology Magnetometer

Data

Radiometric dating

Sediment samples Rheology Magnetometer

Data

Radiometric Dating Radiometric Dating Radiometric dating

Determine age of rocks by looking at half life What is half life?

Found that seafloor rock is significantly younger than rock in the center of the continents Seafloor: 200 million years old Continent: 3.9 billion years old

Why is that?

Where would the oldest crust be located on the sea floor?

Radiometric dating Determine age of rocks by looking at half life

What is half life?

Found that seafloor rock is significantly younger than rock in the center of the continents Seafloor: 200 million years old Continent: 3.9 billion years old

Why is that?

Where would the oldest crust be located on the sea floor?

Sediment Samples Sediment Samples

Coring: drilling holes in the ocean floor for samples Level of sediment

buildup on top of the hard ridge

Question: If you know that the youngest ocean floor is near the mid ridge and older floor is near the trenches (continents) which section of the ocean would you expect to have the most sediment?

Alvin

Coring: drilling holes in the ocean floor for samples Level of sediment

buildup on top of the hard ridge

Question: If you know that the youngest ocean floor is near the mid ridge and older floor is near the trenches (continents) which section of the ocean would you expect to have the most sediment?

Alvin

RheologyRheology

Rheology: Study of how matter flows Measure the

temperature of the ocean water

Where do you expect the temperature to be higher? Near the trenches or ridge?

Temperature of water decreases as you move away from the ridge.

Rheology: Study of how matter flows Measure the

temperature of the ocean water

Where do you expect the temperature to be higher? Near the trenches or ridge?

Temperature of water decreases as you move away from the ridge.

Magnetometer Data Magnetometer Data Magnetometer: measures

the polar orientation and intensity of magnetism of minerals 1961 studied the polar

orientation magnetism of seafloor basalt

Minerals are often magnetic and align themselves to the poles as they settle.

Found a pattern Earth reverses its magnetic

poles and the minerals reflected the switch!

Switched about 10 times over 4 million years.

Magnetometer: measures the polar orientation and intensity of magnetism of minerals 1961 studied the polar

orientation magnetism of seafloor basalt

Minerals are often magnetic and align themselves to the poles as they settle.

Found a pattern Earth reverses its magnetic

poles and the minerals reflected the switch!

Switched about 10 times over 4 million years.

Hydrothermal Vents Hydrothermal Vents

Found on the ocean floor well below the photic zone No sunlight

Many unique life forms: clams, giant tubeworms, crustaceans

How can life survive down there? Heated vent provides

adequate temp for productive ecosystems

High levels of dissolved hydrogen sulfide

Chemosynthesizers

Found on the ocean floor well below the photic zone No sunlight

Many unique life forms: clams, giant tubeworms, crustaceans

How can life survive down there? Heated vent provides

adequate temp for productive ecosystems

High levels of dissolved hydrogen sulfide

Chemosynthesizers

Plate Tectonics Plate Tectonics

Seafloor spreading: explanation of how continents spread

Explanation for Island formations away from plate boundaries!

Seafloor spreading: explanation of how continents spread

Explanation for Island formations away from plate boundaries!

Hot Spots = Island ChainsHot Spots = Island Chains

Hot Spots: areas within mantle where thermal plumes cause magma columns to push up intensely, breaking through crust Hot spots do not move

because they are located within mantle

The plate moves over the hot spot over millions of years forming islands in chains

Hot Spots: areas within mantle where thermal plumes cause magma columns to push up intensely, breaking through crust Hot spots do not move

because they are located within mantle

The plate moves over the hot spot over millions of years forming islands in chains

Types of BoundariesTypes of Boundaries

Divergent BoundaryDivergent Boundary

Divergent Boundary: two plates are moving apart Creation of new

sea floor

Divergent Boundary: two plates are moving apart Creation of new

sea floor

Convergent BoundaryConvergent Boundary

Convergent Boundary: two plates are pushed together Oceanic - oceanic convergence Continental-continental convergence Oceanic - continental convergence

Convergent Boundary: two plates are pushed together Oceanic - oceanic convergence Continental-continental convergence Oceanic - continental convergence

Types of Boundaries Diagrams

Types of Boundaries Diagrams

Convection Convection Convection in the mantel drives seafloor

spreading and continental drift Vertical circulation pattern in a gas or liquid

cause by hot material rising and cold material sinking

Convection in the mantel drives seafloor spreading and continental drift Vertical circulation pattern in a gas or liquid

cause by hot material rising and cold material sinking

Pangea Pangea

Pangea In Action Pangea In Action

Changes are still happening today! Changes are still

happening today!

Florida and the Gulf of Mexico Changes in land mass due to

Continental spreading Rising ocean levels

Formed about 300 million years ago and still forming!

Andes are still forming Pacific Ocean is getting smaller

Florida and the Gulf of Mexico Changes in land mass due to

Continental spreading Rising ocean levels

Formed about 300 million years ago and still forming!

Andes are still forming Pacific Ocean is getting smaller

Florida then and nowFlorida then and now