The Ocean and the Rock Cycle

The Ocean

Oceans, which are large, salty bodies of water, cover about 70 percent of the surface of Earth. The five oceans of Earth are the Pacific, Atlantic, Indian, Arctic, and Southern Oceans.

Ocean water is a complex mixture of:

  • Gases (such as oxygen): marine animals need these for survival to breathe

  • Dissolved solids (salts): salinity, or saltiness, of water depends on evaporation rates and runoff

Ocean Features

  • Continental shelf: the shallow, gently sloped part of the continental crust

  • Continental slope: the steeply sloped edge of the continent

  • Continental rise: the transition between the continental slope and the ocean floor

  • Abyssal plain: smooth, flat regions of the deep ocean floor

  • Ocean trenches: deep pits in the ocean floor caused by tectonic plate movement

Basic Motions of Ocean Water

Waves: caused by wind blowing on the water’s surface

Tides: daily rise and fall of water levels caused by the pull of the moon and sun’s gravity on Earth


  • Surface currents: caused by wind patterns

  • Deep currents: caused by differences in water densities due to salinity and temperature

  • Affect the mixing of ocean waters, which can affect animals and plants

Ocean Life

Plankton: tiny free-floating organisms that live in water

Phytoplankton: plant-like plankton that carry out most of the photosynthesis on Earth and provide much of Earth’s oxygen; they also form the base of the ocean food web

The ocean is home to millions of species, such as kelp, many types of fish, whales, dolphins, and much more.

The Rock Cycle

Types of rocks:

  • Sedimentary: formed by layers of sediment cemented together

  • Igneous: formed through the cooling of lava

  • Metamorphic: formed when heat and pressure transform sedimentary or igneous rocks

The rock cycle shows how the rock types are created and how different processes change rocks from one type to another.

Processes in the rock cycle:

  • Compaction/cementation: pushes sediment together to form sedimentary rock

  • Weathering/erosion: breaks down rock to form sediment

  • Heat and pressure: transforms rocks into metamorphic rocks

  • Melting: causes rock to become liquid lava

  • Cooling: causes lava to form into igneous rock


Sources Used and Helpful Links