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STUDY GUIDE FOR CHAP. 4.1 – EXPLORING THE OCEAN
I. LEARNING ABOUT THE OCEAN
A. TRADING ROUTES
- People have studied the ocean since ancient times because the ocean provided them with _______, _______,
and __________.
B. SCIENTIFIC DISCOVERIES
- As modern science developed and trade increased, ocean exploration changed into developing accurate
______ of continents, countries, and land boundaries.
- Once the world was mapped out, scientists turned their attention to discovering what was in the ______ and
what did the ocean floor look like.
C. EXPLORING THE OCEAN FLOOR
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Studying the ocean floor is difficult because it is so ______ – 3.8 kilometers deep on average.
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Also, sunlight only goes through the surface of the ocean. The rest of the ocean is in _________.
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Lastly, the water is extremely ____ the farther down one goes. The colder the water, the more _______
it exerts.
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A major advance in mapping the ocean floor was ______. Sonar stands for Sound, Navigation, and
Ranging.
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The sonar is on a ship and it sends out ______________ toward the ocean floor.
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Once the sound waves hit the ocean floor, it ___________ back to the sonar on the ship. The time it
took the reflected sound wave to come back tells scientists how _____ the ocean is. (The longer the
time, the deeper the ocean.)
II. FEATURES OF THE OCEAN FLOOR
- The ocean floor is not flat but contains huge __________ ranges and deep __________ bigger than found on
land.
- The landforms found at the bottom of the ocean are the _______________, _____________,
_______________, and _______________.
A. SHALLOW WATER
- The highest point on the ocean floor is the _______________. The continental shelf extends outward from the
shore or continent.
- At about 130 meters in depth, the continental shelf incurs a steep drop. This is called the _______________.
The slope marks the true edge of a continent – there is where the rock of the continent stops and the rock of the
ocean floor begins.
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B. OPEN WATER
- On the ocean floor, you have ______________, _____________, _____________, _____________, and
___________.
- _________________ = Volcanoes on the ocean floor erupted and created mountains. The peaks of the
mountains can break through the water and form an island (such as the Hawaiian Islands).
- _____________ = These are mounts whose peaks do not break the surface of the water.
- _____________ = This is smooth, nearly flat region of the ocean floor. It is thick layers of mud, silt,
sediments, and the dead remains of organisms from the surface.
- ____________ = This is a continuous range of mountains that goes around the entire Earth and surrounds a
central valley in the middle of the ocean floor. It is nearly 80,000 kilometers long and is considered the longest
mountain range on Earth.
C. DEEPEST DEPTHS
- _______________ = These are canyons on the bottom of the ocean floor.
III. MOVEMENTS OF THE OCEAN FLOOR
- When collecting rock samples from the ocean floor, rocks __________ to the mid-ocean ridge are the newest
made rocks. Rocks _________________ from the ridge are older rocks.
- The making of rock at the ridge and moving outward is how the _______________ is made.
A. LAYERS INSIDE EARTH
- The Earth is made up of three layers: the _________, the __________, and the ________.
- The _______ is a solid sphere of metals such as nickel and iron.
- Surrounding the core is the ________. The mantle is liquid rock called magma.
- Surrounding the mantle is the _________. The crust is a thin, flaky layer of rock.
B. EARTH’S PLATES
- The Earth’s crust is broken into 14 irregularly shaped pieces called __________.
- On top of the plates are ________ and _____________.
- The plates move slowly at a speed of several __________ a year.
- Plates can collide in three ways: ____________,_____________, and ____________. This created
mountains, trenches, and earthquakes both on land and on the ocean floor.
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C. PLATES MOVING APART
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The mid-ocean range is located on two plates that are moving _______.
- As the plates diverge, hot magna spills out and hardens along the ridge as a new strip of _______.
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Over a million years, this creates new ocean floor. This process is called _________________.
D. PLATES MOVING TOGETHER
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As new ridges of rock are formed at the mid-ocean range, the older layers of rock are pushed ______
inside the trenches.
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As the rock goes into the trenches, it is send back into the mantle to melt and turn into _______.
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The circular process of seafloor spreading allows the ocean floor to remain the ______ size.
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