Transcript Chapter 23 Worksheets

Chapter 23.1 Studying the Ocean
Floor
Place these answers onto your
worksheets.
Studying the Ocean Floor
1. Echo sounding: Scientists track the
amount of time it takes for a single or
multiple beams of sonar to reach sea
floor and echo back.
2. Sediment sampling: Scientists take
core samplings of ocean sediment in
order to study sediment layers.
3. Satellite observations: Satellites
measure the time it takes a signal to
bounce off ocean surface and
determine ocean floor changes from
differences in surface levels.
Section 23.2 The Continental
Margin
1. Passive continental margin:
Located away from plate boundaries,
passive margins feature broad
continental shelves and fairly gradual
gradients across the continental slope
and rise.
Section 23.2 The Continental
Margin
2. Active continental margin: Located
where continental and oceanic plates
meet, active margins feature narrow
continental shelves, precipitous
continental slopes, and nearly
nonexistent continental rises.
After You Read
Describe how submarine canyons form.
Underwater canyons either date back
to rivers cut through the land in earlier
times when sea levels were lower or
form from the erosion effects of
turbidity currents.
Section 23.3 The Ocean Basins
While You Read
1. Abyssal hill: Small rolling, sedimentcovered hills formed as the sea-floor
surface near mid-ocean ridges.
2. Abyssal plain: Flat area of sea floor
created by sediment brought from
continents by turbidity currents and
then spread out by the sea.
Section 23.3 The Ocean Basins
While You Read
3. Deep-ocean trenches: Long, steepsided troughs parallel to meeting of
lithospheric plates, formed when one
plate subducts beneath another.
4. Mid-ocean ridges: Undersea mountain
ranges formed when lithospheric plates
move apart, allowing magma to rise into
the space and cool.
Section 23.3 The Ocean Basins
While You Read
5. Seamounts/guyots: Cone-shaped
mountain peaks formed originally by
volcanoes; when the sea erodes away
the top, seamounts become guyots.
After You Read
a. Abyssal plain----------Atlantic ocean
b. Abyssal hills-------North Atlantic Ocean
c. Deep-ocean trenches----Indian Ocean,
western Pacific Ocean; Java Trench, Manilla
Trench, Philippine Trench
d. Seamounts--------Hawaiian Islands
Section 23.4 Ocean Floor
Sediments
1. Terrigenous sediments: bits and pieces
of continents; carried by rivers or
icebergs out to sea, particles range from
gravel and sand to tiny grains and
flakes, can travel great distance before
settling to ocean floor.
Section 23.4 Ocean Floor
Sediments
2. Hydrogenous sediments: chemical
reactions cause minerals to crystallize
from seawater, form very slowly on the
sea floor in lumps; found in all oceans
and in some lakes.
Section 23.4 Ocean Floor
Sediments
3. Calcareous oozes: shells and skeletons
of marine animals or plants; containing
at least 30% calcium carbonate;
dissolving into water as they fall; most
common sediment found on half of sea
floor.
Section 23.4 Ocean Floor
Sediments
4. Siliceous oozes: skeletons of marine
life containing silicon dioxide; most
common near equator and around
Antarctica.
Section 23.4 After You Read
Why should we study ocean sediments?
Ocean sediments contain information about
Earth’s history. Sea creatures’ remains tell
scientists about past changes in climate,
water temperature, wind patterns, and
glaciation. Understanding the past can help
scientists predict and prepare for future
changes.