Oceanography and Hydrology

The Southern Ocean (also known as the Antarctic Ocean) was officially recognized as the fifth major ocean by the International Hydrographic Organization in 2000. The other four oceans (Pacific, Atlantic, Indian, and Arctic) have been established and recognized in geography for much longer.

The northern tip of the Bay of Bengal is home to the massive Ganges-Brahmaputra Delta, where rivers regularly flood and deposit rich, mineral-heavy silt onto the land. This process of alluvial deposition creates some of the most fertile agricultural soil in the world.

Red tides are caused by the rapid multiplication of red dinoflagellates like Gonyaulax, which release toxins that can kill marine life.

Diatoms are the chief producers in the oceans. They are microscopic algae that perform photosynthesis and form the base of the marine food web.

Coral reefs are highly sensitive to temperature changes; even small increases can lead to coral bleaching, where corals expel the algae living in their tissues.

Corals have a symbiotic relationship with zooxanthellae, which are photosynthetic algae that require sunlight to produce energy for the coral.

Human activity, such as pollution, overfishing, and climate change, is a primary driver of coral reef degradation globally.

Coral reefs are known as the rainforests of the sea because they support a disproportionately high level of biodiversity despite occupying a small fraction of the ocean floor.

An archipelago is a chain or group of islands. Reefs are underwater structures, while monsoons and tsunamis are weather or geological events.

The water table is the upper surface of the zone of saturation, where the pores and fractures of the ground are completely filled with water.

Freshwater accounts for approximately 2.5 to 3 percent of all water on Earth. Among the choices provided, 2 percent is the closest approximation.

While the ocean contains the vast majority of Earth's water, it is saline. The majority of accessible liquid freshwater is stored in underground aquifers.

The hydrosphere encompasses all water on Earth, including oceans, rivers, lakes, groundwater, and moisture in the atmosphere.

Oceans, lakes, and streams are the primary natural bodies of water on Earth.

The hydrosphere encompasses all water on Earth, which covers approximately 70 percent of the planet's surface. The other options describe the biosphere, atmosphere, or lithosphere.