PHYS 203 Earth In Space Exam II

Why are oceans and coastlines dynamic?

They are constantly changing. Ocean patterns influence heat distribution and coasts are influenced by erosion/deposition.

About how long ago were the oceans set in place?

4 Billion Years Ago

Bathymetry

Measurement of the depth to the ocean floor and mapping of its features; Done by using data gathered by ships and satellites.

The ocean floor has mountains, valleys, and plains similar to those on land.

True

What do masses of rocks do on the ocean floor?

Exert a gravitational pull causing the water to pile up and form a mound.

How does the volume of ocean water compare to the volume of the continents above sea level.

Ocean water is 10x larger.

4 Major Depth Zones

Continental shelf, abyssal plain, oceanic ridge, and oceanic trenches.

Passive v.s Active Continental Margins

Shelf, Slope, Rise for passive; Trench for active, and plain.

What is known about the Mariana Trench?

It is 7 miles deep, located in the Ring of Fire, and is composed of 2 oceanic convergent plates.

What is the average salinity of seawater?

35% or 35 parts per thousand.

What elements constitute the salts in the ocean?

Mainly sodium and chloride among other trace amounts of elements.

Sources of Sea Salts

Chemical weathering of rocks and gases from volcanic eruptions.

What affects seawater salinity?

Process that change the water content of the solution.

What processes decrease water salinity?

Precipitation, runoff, icebergs melting, and sea ice melting.

What processes increase water salinity?

Evaporation and formation of sea ice.

What other factors affect salinity?

Temperature, mixing caused by currents, and freshwater input from rain, streams, and melting ice.

Where is salinity the highest?

Where temperature is high and precipitation is low.

3 Ocean Layers

Surface mixed zone, transition zone, and deep zone.

Halocline

Rapid change in salinity with depth.

Deeper waters are not affected by surface processes that change salinity.

True

What variables affect ocean temperature?

Latitude, depth, solar insolation, and ocean currents.

Where are ocean temperatures highest?

Where solar energy is highest.

What is known about the specific heat of water?

It is very high meaning water’s temperature takes a lot of thermal energy to change.

How does the density of water change with temperature?

Density decreases as temperature increases.

Thermocline

Rapid change in temperature with depth.

What layers does the thermocline divide?

Upper mixed layer from the calm deep water below.

What 3 factors create the ocean’s density profile?

Salinity, temperature, and pressure.

How does pressure affect ocean density?

Increase of pressure with depth slightly increases the density of the water below it.

Pycnocline

Rapid increase in density from 200 to 1000 meters down.

Density is uniform below the pycnocline.

True

What is the ratio of the ocean’s 3 main density layers?

Surface 2%, middle 18%, and bottom 80%.

Where is the pycnocline absent?

In oceans where the latitude is high.

3 Ocean Light Zones

Photic, Euphotic, and Aphotic

Gyres

Circular patterns of ocean currents.

How does ocean water follow currents?

Currents follow prevailing wind direction except where the current encounters a barrier like a landmass; Only about 10% of ocean water is moving in surface currents.

Continents can affect ocean circulation patterns.

True

Gulf Stream Thermohaline Circulation

Carries high salinity warm water from mid Atlantic to higher latitudes, then water cools as it travels north, then cold salty water sinks around Greenland/Iceland, then sinking water is carried south along the bottom of the Atlantic, then reaches Antarctica and is diverted to India/Pacific ocean, then deep current eventually comes up in North Indian and Pacific oceans bringing nutrients to the surface (Upwelling).

Thermohaline

Pattern of deep currents driven by salinity and temperature.

How long is the moon’s orbit around Earth?

27.3 Days

How long is the moon’s rotation?

27.3 Days

New Moon

Moon between Earth and Sun

Full Moon

Earth is between the Sun and Moon.

Tides

Changes in the sea surface height caused by the moon’s gravitational attraction.

Spring Tides

Largest tidal bulges/Highest tides

Neap Tides

Smallest tidal bulges/Lowest tides

How do water particles move in the ocean?

They follow a circular path while remaining in place. The water simply bobs up and down while the waveform moves through it.

What controls wave size, speed, and direction?

Wind

Wavebase

Downward distance equal to one half the wavelength; Here water motion decreases drastically.

What happens to a wave as it approaches the shore?

It gets consumed by friction; The wavelength decreases, the wave becomes taller, and it moves slower.

What can cause refraction of waves towards the shore?

Irregularities in the shoreline or changes in the seafloor.

Spit

Sand bar partially blocking a landform.

Baymouth Bar

Sand bar that completely blocks a channel.

How can a shoreline grow?

With the deposition of sediment.

What do longshore currents do?

Transport sediment parallel to the beach in the surf zone.

What are different types of plankton?

Zooplankton, Floaters, Phytoplankton, and Bacteria.

Nekton

All animals capable of moving independently of the ocean currents; They are unable to move throughout the breadth of the ocean.

Fault

Fracture in the crust on which movement has occured; Zone of weakness where Earthquakes occur.

Focus

Location where movement begins on fault.

Epicenter

Location on surface above the focus.

Fault Scarp

A “step” in the land surface caused by the movement on the fault.

Only part of a fault breaks during an earthquake.

True

Seismic Waves

Vibrations caused by earthquakes; Travel in all directions from the focus.

Slow Surface Waves

Responsible for most earthquake damage; Rayleigh waves result in vertical movement of the surface while Love waves produce a side-side movement of the surface

Fast Body Waves

Travel through Earth’s interior; P waves compress like a slinky and S waves account for vertical displacement

How can Earthquake size be determined?

By measuring the amplitude of the seismic waves.

How can Earthquake distance be measured?

By observing the arrival times between the S, P, and surface waves; Time increases the further away the earthquake is.

How is magnitude measured?

On a logarithmic scale

How is intensity measured?

Using the modified Mercalli scale

What makes it difficult to compare earthquakes from different regions?

Population density, building codes, ground materials, and distance.

What are some hazards associated with earthquakes?

Ground shaking, aftershocks, landslides, elevation changes, liquefaction, and tsunami’s.

How can ground shaking be dependent on the Earth material?

Less shaking for bedrock and more shaking for mud/sand.

Where are landslides common?

Steep Slopes

How do elevation changes occur?

Movement on faults.

How do tsunami’s form?

Fault displacement of ocean floor displaces large volume of water; Associated with subduction zones

3 Types of Volcanoes

Shield, Strato, and Cone

Shield Volcano

Gentle slopes with basalt; Associated with divergent plate boundaries and hot spots.

Strato Volcano

Most common volcano type; Steeper slopes built from alternating layers of tephra and andesite; Form on plates overriding subduction zones at convergent plate boundaries

Cone Volcano

Smallest Volcanoes; Built from viscous magma products

What controls how easily gas escapes from magma?

Magma Viscosity

What does magma viscosity depend on?

Temperature and magma composition which depends on plate tectonic setting; Less silica means lower viscosity and more silica means higher viscosity

What gases are dissolved in magma?

Water vapor, carbon dioxide, and sulfur dioxide.

What determines violent eruptions?

More pressure is required to remove gas from more viscous magma; Higher viscosity means more violent eruptions

Where are the most active volcanoes found?

Near convergent plate boundaries.

Basaltic Magma

Partial melting of asthenosphere below oceanic ridge and hotspots.

Rhyolitic Magma

Melting parts of continental crust

Andesitic Magma

Partial melting of mantle rocks at subduction zone.

Which minerals will have the lowest melting temperatures?

Silica rich minerals.

Tephra

Particles blasted into the air by the eruption.

Pyroclastic Flow

Dense cloud formed from combination of tephra and volcanic gases.

Lahars

Mudflows formed when volcanic debris mixes with streams or melting ice.

How does viscosity affect lava distance?

Lower viscosity lava travels farther while higher viscosity lava remains within the volcano crater.

Caldera

Giant crater formed from the collapse of a volcano into underlying magma chamber.

What phenomenae do plate tectonics form?

Earthquakes, volcanoes, mountain belts, and features on the seafloor.

How does oceanic crust differ from continental crust?

Oceanic crust is denser and thinner.

Plutonic Rock

Magma that cools and solidifies below the surface.

Volcanic Rock

Magma that cools and solidifies at the surface.

How does rapid/slow cooling differ?

Rapid cooling creates small microscopic crystals while slow cooling creates large visibile crystals.

3 Types of Plate Boundaries

Divergent (Mid-Atlantic Ridge), Convergent (Subduction Zones/Ring of Fire), and Transform (San Andreas Fault)

Law of Superposition

Oldest rocks are at the bottom.

Principle of Original Horizontality

Sediment is deposited horizontally.