Ocean Geography & Earth
About what percentage of Earth's surface is covered by water?
71%
Who proposed the continental drift hypothesis?
Alfred Wegener
What gently sloping underwater extension of a continent begins at the shoreline?
Continental shelf.
What is the approximate bond angle that gives a water molecule its bent shape?
105°.
What term describes the total amount of dissolved salt in seawater?
Salinity
Name all five oceans.
Pacific, Atlantic, Indian, Southern, Arctic.
What was the name of the supercontinent that Wegener proposed once contained today's continents?
Pangaea
Put these in order moving from the coast toward the deep ocean: abyssal plain, continental rise, continental shelf, continental slope.
Shelf → slope → rise → abyssal plain
What property results from unequal electron sharing within a water molecule?
Polarity
What happens to seawater density when salinity increases?
Density increases
Put Earth's four major layers in order from outside to inside.
Crust → mantle → outer core → inner core
What process creates new oceanic crust at mid-ocean ridges?
Seafloor spreading.
What deep valleys cut into continental shelves and slopes can be carved by turbidity currents?
Submarine canyons
What attractive forces occur between neighboring water molecules?
Hydrogen bonds.
What is the difference between a thermocline and a halocline?
A thermocline is a rapid change in temperature with depth; a halocline is a rapid change in salinity with depth
Which core layer is liquid, and what important Earth feature does its movement generate?
Outer core; Earth's magnetic field.
What evidence on opposite sides of mid-ocean ridges provides strong support for seafloor spreading?
Parallel, symmetrical magnetic stripes.
Why is the continental rise usually more developed along a passive margin than an active margin?
Passive margins allow thick sediment accumulation, while active margins may have trenches that intercept sediment.
Why does ice float on liquid water?
Hydrogen bonds arrange water molecules into an open crystalline lattice as water freezes, increasing volume and making ice less dense than liquid water.
According to the principle of constant proportions, what remains generally constant even when total ocean salinity changes?
The relative ratios of the major dissolved ions.
Compare oceanic and continental crust using composition, thickness, and density.
Oceanic crust is primarily basaltic, thinner, and denser; continental crust is primarily granitic, thicker, and less dense.
New oceanic crust continuously forms at ridges. Why doesn't Earth continually grow larger?
Older oceanic crust is recycled into the mantle through subduction at convergent boundaries.
A research vessel discovers a very deep, narrow depression immediately offshore accompanied by frequent earthquakes. What tectonic process most likely explains this feature?
Subduction at an active/convergent plate boundary, producing an ocean trench.
Explain the chain connecting water's molecular shape to its ability to stabilize ocean temperatures
Bent shape → unequal charge distribution/polarity → hydrogen bonding → high specific heat/thermal buffering → oceans absorb large amounts of heat without rapid temperature changes.
Two water masses have the same volume. Water Mass A is warm and less salty; Water Mass B is cold and saltier. Which is more likely to sink, and why?
Water Mass B because colder temperatures and higher salinity both increase seawater density.