Marine Science Chapter 2

What is the crust of the earth

Outermost layer of earth made of solid rock

What is the mantle

underneath the crust, hot, semi-solid rock, capable of slow movement

What is the core

make up the center of the Earth; hot, dense, and under great pressure

Which part of core is liquid, which part is solid

Inner core is liquid, outer core is solid

Theory of continental drift

over 300 million years ago all the continents were connected to form “Pangea”

3 pieces of evidence used for continental drift

• Similar fossils of plants and animals are found on continents that are separated by oceans.
  • Similar geological structures (rock layers in South Africa match those in Brazil)

• The shoreline shape of continents with similar geological features seem to fit like a jigsaw puzzle.

Theory of plate tectonics

suggests that lithosphere is broken
into sections called plate tectonics which move on top of mantle

Evidence of plate tectonics

• distribution of fossils

• geologic matching of rock formations

• jigsaw-like fit of continents

• paleomagnetic st

What are convection currents

movement of fluids or air based on density difference caused by differing temperatures

3 steps for formation of convection currents

1. As magma heats up its molecules spread out, becomes less dense, and rises above cooler magma

2. Near the asthenosphere magma cools and begins to sink

3. This forms a circular cell of molten rock capable of moving the lithosphere plate above it

Features at transform boundaries

• Earthquakes

• Tsunamis

Features at convergent boundary

• Trenches

• Volcanoes

Features at divergent boundary

• Earthquakes

• Ridges

• Hydrothermal vents

How do volcanoes form at convergent boundary (4 steps)

1. Plate subducts and is exposed to friction

2. This causes rock to melt

3. Melted rock is less dense and rises to surface

4. This forms volcanoes ob non-subducting plate

How do volcanoes form at divergent boundary (3 steps)

1. Crust pushes away from the ridge

2. This movement causes small cracks to form on ocean floor

3. Magma rises to surface through cracks and forms volcanoes

Explain the movement of two plates at convergent boundary

1. Oceanic plate subducts under the continental plate

2. Oceanic plate is more dense than continental plate

Compare oceanic and continental plate

• Oceanic plate is slimmer but more dense than continental plate

• Continental plate is thicker and made of granite

• Oceanic plate made of basalt

Steps for earthquakes to form

1. Energy is released from seabed

2. All water moves above seabed

3. Water holds onto energy and moves very quickly through deep water

4. Water gets to shallower water and slows down but height grows very tall

Steps for hydrothermal vents to form

1. Cold water seeps through cracks in thin crust surrounding divergent boundaries

2. Water flowing into a magma chamber dissolves mineral from rocks 

3. Super heated water coming from hydrothermal vents is under pressure, hot and rich in dissolved nutrients and this forms hydrothermal vent plume

4. Superheated water meets near freezing ocean floor and cools

5. Minerals precipitate out of solution (solidify and pile on top of each other)

6. This causes a vent/chimney for the water and can be 60m high

What is an abyssal plain

Flat, sandy region of the ocean floor found at transform boundaries or between boundaries

How do abyssal plains form

1. As new seafloor is formed the old rock is pushed further and further away

2. Over time the rocks are covered with sediment and organic material

What are paleomagnetic stripes/magnetic polarity reversal

• Measured the magnetism of the ocean using magnetometers

• Earths crust is laid out in alternating stripes of normal polarity and reversed polarity

• Evidence shows that striped pattern began at mid ocean ridges where crust is weakest and magma pushed through

Compare chemical and physical weathering in marine environments

• Chemical weathering changes the rock’s composition chemically

• Physical weathering breaks rocks into smaller pieces without chemical change

Characteristics of chemical weathering

• Caused by reactions with water and oxygen

• Releases dissolved minerals into the ocean

Characteristics of physical weathering

• Caused by temperature changes or wave action

• Increases sediment size and volume

Describe how sedimentation shapes muddy shores

• Muddy shores are found in protected areas with little wave or current action

• Fine sediments like silt settle out of suspension due to low water movement 

• Sedimentation is the main process responsible for the formation of muddy shore

Explain how deltas form at the mouths of rivers

1. Rivers pick up sediment as they flow downstream

2. As the river widens at the mouth, water slows down

3. Sediments settle to the bottom, forming sandbars

4. Over time, the buildup forms a fan shaped delta with possible tributary channels

Identify and describe two types of erosion and how they transport sediment

• Ice erosion: glaciers crush rock and transport sediment within or on top of the ice

• Water erosion: rivers and runoff carry sediment to the ocean

Explain how erosion and sedimentation work to form estuaries

• Estuaries are sheltered from strong wave action so very little erosion occurs

• The water is calm, allowing fine particles like silt and sand to settle (sedimentation) 

State two reasons why rock shores are resistant to erosion

• Made of granite which is resistant to weathering

• Open and exposed, but rocks are large and tightly packed

Explain how water erosion can contribute to sedimentation in marine environments

1. Water erosion picks up and carries sediments through rivers and runoff

2. As water slows (when it reaches ocean) sediments begin to settle

3. Larger particles settle first while finer particles may stay suspended and travel further

Identify the main processes involved in shaping sandy shores and describe how they affect the shoreline

• Wind and wave erosion: moves sand along the beach and up and down the shore

• Gradual slope forms due to loose sediment settling and constant motion

• These processes constantly shift and reshape the shoreline 

Compare estuaries and deltas in terms of their formation and environmental conditions

• Estuaries form where freshwater meets saltwater in partially enclosed body; deltas form where a river deposits sediment at its mouth

• Estuaries have brackish water and are sheltered from waves; deltas are more open and subject to sediment build up

• Estuaries are turbid and nutrient-rich due to fine sediments; deltas are shaped by sediment slowing and settling

Describe how sediment size and water speed affect deposition

• Faster-moving water can carry larger particles

• As water slows larger particles settle first

• Fine particles like silt can stay suspended longer and travel farther

Describe the 4 types of erosion

• Ice erosion: glaciers drag and crush rocks, carrying sediment embedded in ice

• Gravity erosion: rocks fall from cliffs and move toward the ocean

• Wind erosion: wind blows sand or dust from one place to another

• Water erosion: rivers and runoff carry sediment into the sea

Explain how the morphology of a rocky shore affects sedimentation

• Rocky shores are steep and made of resistant granite

• High wave energy removes loose particles before they settle

• As a result, very little sedimentation occurs on rocky shores

Explain how tides are produced

Tides are the periodic rise and fall of the surface of the ocean resulting from the gravitational interaction of the earth with the moon and sun

Identify and describe two types of tidal patterns

Semi-diurnal: tides that occur twice a day (two high and two low tides)

Diurnal: tide occurs once a day (one high and one low)

What is tidal range? What causes it? How is it calculated?

• Tidal range: difference in tide height between consecutive high and low tide

• Caused by gravitational pull of sun and moon and difference

• High tide - low tide = tidal range

Describe and explain what causes a spring tide to form and how often do they occur?

• Describe: spring tides occur when the earth, sun, and moon are aligned (new moon and full moon)

• Explain: the alignment amplifies the gravitational effect the moon and sun have on earth

• Spring tides occur twice a month

Describe and explain what causes neap tides to occur and how often do they occur?

• Describe: occur when the sun and moon are at right angles from each other

• Explain: sun and moon are pulling at opposite directions causing a smaller than average tidal range

• They occur twice a month

Describe how the alignment of sun, moon, and earth cause tidal range seen with spring tides

• tidal range = high tide - low tide

• When earth, moon, and sun are in straight line gravitational effects of sun and moon combine and cause stronger tides

• greater tidal range = spring tides

Describe how the alignment of sun, moon, and earth cause tidal range seen with spring tides

• Tidal range = high tide - low tide

• When moon and sun are at a right angle with earth gravitational effects are working against each other causing weaker tides

• Smaller tide range = neap tides

State 3 factors, other than gravitational effect on moon and sun, that could influence tidal range

• shape of coastline

• size of body of water

• weather conditions

Explain how the shape of the coastline could influence tidal range

• If the tide enters a narrow channel or bay the tidal height is increased because water is being forced into small area

• Along an ocean beach the tide height is not increased due to water being more spread out

Explain how weather could influence tidal range

• During tropical cyclones the air pressure is much lower and allows the water to swell; high winds also push water onto the shore

• High winds and low air pressure can create a tidal surge (rising water higher than the predicted level of the tide)

Define ocean currents

A continuous physical movement of water caused by wind or density

What are surface currents caused by

Surface currents are driven by wind (caused by uneven heating on earth’s surface)

What factors cause deep currents to form

Deep currents are driven by difference in density as temperature and salinity changes

Describe the Coriolis effect

• It is a result of earth’s rotation causing wind and objects to be deflected toward left or ight and now travel in straight pattern

• This also causes surface currents to be deflected at a 45-degree angle

Describe thermohaline circulation

1. Starts in N pole when cold water freezes to ice-leaving salt behind

2. Denser water down wells, mixed with water column until its at the bottom

3. In Antartica water gets colder and then splits

4. One current goes to Indian ocean and one current goes to pacific ocean

5. Water near equator warms/rises

6. Both warm currents go north in Atlantic towards the N pole

Describe the movement of surface currents in the northern and southern hemisphere

• Northern hemisphere currents have clockwise spiral

• Southern hemisphere currents have counter clockwise spiral

• As wind blows water across the ocean, the rotation of earth causes it to deflect at 45 degree angle (Coriolis effect)

Describe upwelling

• Movement of cold nutrient rich water from deep ocean to the surface

• Caused by warmer water being pushed away from the coastline causing low-pressure area that brings colder water to the surface

Describe the movement of surface water in the south pacific ocean during normal conditions

Winds-westerlies blow water away from south coast of South America and towards Australia and Asia

Describe the condition of South Pacific Ocean during El Nino years

• Warm water builds up along the coast of S America preventing upwelling (decline in productivity)

• Trade winds around the equator reduce/slow down and prevent warm water & moist air from moving west

• Indonesia and Australia experience drought conditions/Peru and eastern pacific have increased rainfall

What is El Nino and where does it occur

El Nino is a warm current and it develops off the coast of Ecuador in December

What is La Nina

• Cold current

• Develops off the coast of Ecuador and spreads across the Pacific

• Reduces sea surface temperatures for extended periods of time

Describe the effect La Nina has on upwelling compared to El Nino

• El Nino suppresses upwelling 

• La Nina allows for more cold water from Humboldt current to rise to the surface

• Stronger upwelling than normal more than average nutrients surface to the top of the ocean

• This leads to a greater ocean productivity

Explain the effect El Nino has on the fish harvest for fisherman in Eastern Pacific

• Reduction in upwelling of cold deep nutrient rich water off cost of Peru

• Less nutrients in water lowers phytoplankton productivity

• This will cause a reduction of food for sardines population and less sardines stock

• Weaker east pacific current causes an increase in temp of coastal waters and causes a decline in cold-water species

Explain the effect El Nino has on the weather of New Zealand coast in the southern pacific

• Decline/lower temps in New Zealand coastal regions

• Because the weaker east pacific currents don’t bring warm waters to New Zealand

Compare El Nino conditions with normal conditions in southern Pacific

During El Nino trade winds change direction, moving ocean surface water from west to east from Australia to South America

Explain why there’s a small fish harvest during El Nino years

• No upwelling

• Less nutrients for producers causing decline in phytoplankton

• This causes a decline in fish population

• Cold water fish cannot adapt to changes in water temp

• As upwelling is suppressed, warm water builds up at the surface of the ocean