Oceans Characteristics

Features Life Forms

The World’s Oceans

n  71% of the Earth’s surface is covered by water.

n  The oceans contain 97% of the

earth’s water.

n  Oceanographers are scientists who study the ocean and its processes.

Oceans n The oceans are the Atlantic, Pacific, Indian, and Arctic.

n The Pacific Ocean is the largest ocean.

Importance of Oceans

• Oceans affect all living things—even those far from the shore.

• Oceans provide a place for many organisms to live.

How were the oceans formed? n  When Earth was still a young

planet, many active volcanoes existed. As they erupted, lava, ash, and gases were released from deep within the Earth.

n  One of these gases was water vapor.

Formation of Oceans

• Over millions of years, the water vapor cooled enough to condense and form clouds. Then torrential rains began to fall from the clouds.

n  Eventually, much of the land was covered by water that formed

Salinity n  Salinity describes the

amount of dissolved salt in the ocean.

n  Salinity plays a vital

role in ocean currents because dense water sinks below less dense water.

n  More salt = more

density

Waves

•  A wave in water is a rhythmic movement that carries energy through the water.

•  Waves are caused by high winds blowing on top of the water.

Tides • Throughout a day, the water level

at the ocean’s edge changes. This rise and fall in sea level is called a tide.

• Tides are created by the gravitational attraction of Earth and the Moon and of Earth and the Sun.

Tides • Tides are created by the gravitational attraction of Earth and the Moon and of Earth and the Sun.

The Ocean Floor n  The ocean floor has higher

mountains, deeper canyons, and larger flatter plains than on land.

n  Earthquakes occur more often. n  The rocks are very different. n  The crust is thinner.

How do scientist know the landforms are there?

n  Bathymetric maps of the ocean floor are created by collecting and plotting depth measurements

n  Depth measurements are taken by sonar (echo sounding)

n  Sonar are sound waves that are sent from the ocean surface to the ocean floor. The amount of time it takes for the sound to travel down and back is one depth measurement.

How do scientist know the landforms are there?

n  Variations in depth are used to infer or explain elevations and depression in the ocean floor.

n  Depth measurements compiled together make a depth profile.