Investigating Oceanography - Ch. 2 & 3

The crust is about _____ times as dense as the rock we walk on at the surface.

5 times

What important metals are found in manganese nodules?

Cobalt, manganese, copper, and nickel

Why do oceanographers use sound rather than light to measure ocean depths?

SONAR—is used to find and identify objects in water. It is also used to determine water depth (bathymetry). Sonar is applied to water-based activities because sound waves attenuate (taper off) less in water as they travel than do radar and light waves.

The deepest earthquakes are located at _________ ________ and are no deeper than about ______ km

convergent boundaries; 700

Earth's surface consists of a thin, rocky layer called the ____ and it's about _______ of Earth's mass

crust; 0.4%

In the 1950's a worldwide effort was made to examine the ______ _____ _______

deep-ocean floor

Curie point (study this more)

roughly 580 degrees C

The areas on the surface where body waves do not travel directly are called

shadow zones

The speed and the distance body waves travel depends on

the characteristics of the material they travel through

How deep is the mantle?

2900 km thick Comprises 84% of Earth's volume and roughly 68% of it's mass

The core accounts for ______% of the Earth's volume, but over ____% of it's mass.

15%; 30%

What is a Wadati-Benioff zone?

A dipping zone of seismicity. The deepest earthquakes in the world occur in this zone (up to 650 km deep).

Describe the ridge-push, slap-pull model of plate driving force

A proposed mechanism for seafloor spreading. It assumes convection in the mantle, heating the seafloor. The heating decreases the seafloor density, causing it to expand, creating a mid-ocean ridge. New parts of a plate rise because they are warm and the plate is thin. As hot magma rises to the surface at spreading ridges and forms new crust, the new crust pushes the rest of a plate out of its way. This is called ridge push. Old parts of a plate are likely to sink down into the mantle at subduction zones because they are colder and thicker than the warm mantle material underneath them. This is called slab pull.

Distinguish between a ridge and a rise?

An oceanic ridge is an underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary. The continental rise is an underwater feature found between the continental slope and the abyssal plain. it represents the final stage in the boundary between continents and the deepest part of the ocean.

Locate the boundaries of the 7 major plates

Australian Plate, North American Plate, Eurasian Plate, African Plate, South American Plate, Pacific Plate, Antarctic Plate

What is the average rate of seafloor spreading?

Between 1-20 cm per yeah but generally between 2-10 cm per year.

(Ch. 2.5) Where are the 3 main types of plate boundaries and what is the relative motion between plates on each one of them?

Divergent (move apart) Convergent (move together) Transform (slide past)

Most transform faults join what type of plate boundaries together?

Divergent boundaries

By carefully observing when and where body waves created by earthquakes all over the world are recorded, it is possible to create models of

Earth's interior

What is a magnetic reversal, and how is it recorded in seafloor rock?

Earth's magnetic field gradually decreases in strength by a factor of about ten over a period of a few thousand years.

the points on Earth's surface directly above the actual earthquake location, which is called the earthquake focus or hypocenter

Epicenter

How do earthquake patterns, seafloor heat flow, age of Earth's crust, and thickness of seafloor sediments help to support the idea of seafloor spreading?

Epicenter zones were found to correspond to the areas along ridges, trenches, and spreading centers. The rocks from the sea floor convection areas are young and short-lived.

Describe the 3 different ways to classify marine sediments

Gravel, sand, and mud

Does satellite altimetry measure ocean depth directly or indirectly?

Indirectly. Satellite radar altimeters measure the ocean surface height (sea level) by measuring the time it takes a radar pulse to make a round-trip from the satellite to the sea surface and back.

What causes convection cells in Earth's mantle?

Low density molten material heated by Earth's natural radioactivity and heat from the core

What modern landmasses made up Laurasia and Gondwanaland?

N. America and Asia=Lauraisa Africa, S.America, India, Australia, and Antarctica=Gondwanaland

What modern landmasses made up Pangaea?

N. and S. America, Europe, Africa, Antarctica, India, Australia, Asia

Where are the major deep-sea trenches? What is the deepest and longest trench in the world?

Near island arc systems. Deepest: Mariana Trench at 11,020 meters. Longest: Peru-Chili Trench at 5,900 km

What is the difference between a fracture zone and a transform fault?

No movement or earthquake activity occurs along the fracture zone, however, there is relative motion and seismicity along the transform fault between adjacent segments of ridge crust

What are the three types of convergent boundaries?

Ocean to ocean Ocean to continent Continent to continent

What are the two kinds of crust and their differences:

Oceanic- denser and thinner, 5-10 km thickness. Basalt Continental- low in density, 30-50 km thickness. Granite.

What resources account for the vast majority of the monetary value of all resources extracted from the ocean?

Oil and gas

Describe the difference between passive and active continental margins

Passive margins are found where the continent-ocean transition is not a plate boundary. They're relatively wide with little seismic activity. The active margins are found where the continent-ocean transition IS a plate boundary. Active margins are usually relatively narrow with earthquakes and volcanism.

What seafloor resource is used in the production of fertilizer?

Phosphorite can produce phosphate fertilizer

Through what type of materials will P-waves and S-waves travel?

Primary waves travel through solid, liquid, and gas Secondary waves can only travel through solids, not liquids or gases.

List the main provinces and features of the ocean basin floor

Sediments, mid-ocean ridges, continental margins, submarine canyons

How are the outer core and inner core similar? different?

Similar: Different: Outer core is liquid and Inner core is Solid

How can small particles sink quickly to the sea floor?

Smaller particles attract each other owning to their electrical charges. This attraction forms larger particles, which sink more rapidly.

What are the two basic kinds of waves?

Surface waves (do most damage to property, but do not indicate much below the surface) Body waves (cause less damage, but are far more useful in studying Earth's interior)

Where and what is the Moho?

The Moho is the mantle beneath the crust, consisting of rock, denser than crust (due to increase in pressure, not different rock type)

Compare the Panthalassa Ocean and the Tethys Sea

The Panthalassa was one giant single ocean. The Tethys was a much smaller ocean, between Australia and Asia.

What is lysocline?

The depth at which calcareous skeletal material first begins to dissolve

Identify the different parts of the continental margin

The edges of the landmasses below the ocean surface and the steep slopes that descend to the sea floor.

Explain the formation of an atoll

The formation of an atoll begins when an underwater volcano erupts, creating a volcanic mountain beneath the surface. When this mountain builds up and approaches the surface, its rough edges provide an ideal surface for coral to develop. Over time, a circular coral reef builds around the mountain. However, this kind of volcanic rock tends to be soft and porous. The ocean gradually erodes it away, leaving behind a circular reef and a large lagoon. The chemistry of the new lagoon, however, is acidic and kills the coral on the inside. This coral is pounded into sand by water action, and the sand covers and insulates the still-living coral, creating a sandy atoll island over time.

Explain the evidence Alfred Wegener used to propose the theory of drifting continents.

The geographic fit of the continents, Fossils Mountain ranges of similar age, structure, and rock, unusual sequences of rocks and rock units of similar age and chemistry, and patterns of glaciation.

What was the primary objection some scientists had to Wegener's theory?

The inability to identify a mechanism that could cause the continents to break apart and drift through the ocean basins

How can hotspots be used to measure the speed and direction of plates?

The oldest hotspot becomes a guyot (flat-topped seamount) and the newest peak ip above the hot plume.

Describe the stages of the Wilson cycle

The opening and closing of ocean basins caused by movement of the Earth's plates. The Wilson cycle begins with a rising plume of magma and the thinning of the overlying crust. As the crust continues to thin due to extensional tectonic forces, an ocean basin forms and sediments accumulate along its margins.

How do the patterns of magnetic reversals in seafloor rocks verify seafloor spreading?

The polarity and age of the magnetic stripes on a map corresponded to the same magnetic field changes formed in the dated layers on the land. p.64

How are sand and gravel used as a valuable resources both directly and indirectly?

The sediments transform into rocks and preserve the layering of sediment. Sand and gravel are used for road construction, for mixing with asphalt, as construction fill, and in the production of construction materials like concrete blocks, bricks, and pipes. It is also used to make roofing shingles, used on icy roads in the winter, for railroad ballast, and water filtration.

In the Hess model, how do convection cells cause seafloor spreading?

The upward-moving mantle rock would carry heat with it toward the surface and cause the overlying crust to expand. This expansion creates a mid-ocean ridge and active volcanism. Hess proposed that the trenches are areas where the lithosphere depends back into Earth's interior. The lateral movement that is caused by the lithosphere being dragged to the descending sides of the convection cells produces seafloor spreading.

Why is the crust thicker under mountain ranges?

This crust is older

What is the difference between passive and active continental margins?

When a continent rifts and moves away from a spreading center, the resultant continental margin is passive. Active continental margins are often marked by ocean trenches where oceanic lithosphere is subjected beneath the edge of the continent.

What is the relationship between a) crust and mantle b) lithosphere, asthenosphere, and mesosphere

a)Crust is light colored, low-density rock and Mantle is dark-colored, heavy rock. b) The lithosphere is underlain by a weak, deformable region in the mantle called the asthenosphere. The mesosphere is all solid, but convects slowly, moving upward and downward.

What is a hotspot?

an isolated area of volcanic activity. they are formed in the center of plates and at mid-ocean ridges. lifespan is 200 million years.

Hydrothermal vents along mid-ocean ridges are often the site of what natural resource?

cobalt, gold, copper, and rare earth metals essential for electronic components

It is the _____________, broken into roughly a dozen large pieces, that comprises the plates of plate tectonics

lithosphere

Where are most divergent plate boundaries found?

ocean basins

As Panthalassa became smaller, what ocean did it eventually form?

the southern Indian Ocean

List reasons why gas hydrates are important

they are a potential energy source, the contribute to slumping along continental margins, and they may play a role in climate change

What is the difference between the lysocline and the CCD (carbonate compensation depth)?

they will differ in depth depending on the rate of biological productivity and the production of calcareous material. The CCD is also defined as the depth at which the rate of accumulation of calcium carbonate is equal to the rate at which it is dissolved.