Oceanography and Hydrology

The operative word in this sentence is ‘while’, which highlights two contrasting situations. The word that replaces the blank should be opposite to 40 or 50 feet (high). “Few” and “meager” both fits our prediction. But “meager” is usually used to denote poor quality or small amount, inadequate, it will not be coherent if we use it with inches. Hence, (3) is the answer.

Algal bloom in the coastal areas due to increased nutrient loading from human activities is known as red tide. It is caused by a few species of dinoflagellates and is potentially harmful to human health. Red tide toxin can contaminate marine life and humans can become seriously ill by consuming them.

Ocean currents are primarily driven and modified by the Earth's rotation (Coriolis effect), atmospheric pressure and wind patterns, and differences in water density (temperature and salinity). The Earth's revolution affects seasonal cycles but does not directly modify the mechanics of current flow.

A seamount is an underwater mountain rising from the ocean floor that does not reach the water's surface, typically defined as having a height of at least 1000 meters. The mention of 1 meters in the question is a typographical error for 1000 meters.

A fjord is a deep, narrow, and elongated sea inlet with steep sides, created by a glacier carving a U-shaped valley that was subsequently flooded by the sea. Ria coasts differ because they are formed by the submergence of river-cut valleys rather than glaciated ones.

Ocean salinity increases when water is removed via evaporation and not replenished by precipitation. High temperatures accelerate evaporation, and low rainfall ensures the salt concentration remains high.

Ocean currents are modified by the shape of the coastline, seasonal winds, and the topography of the ocean floor. Tidal waves are periodic oscillations caused by gravitational forces and are not considered a primary factor that modifies the steady flow of ocean currents.

The thermocline is the transition layer in a body of water where the temperature changes more rapidly with depth than it does in the layers above or below. It effectively separates the warm, well-mixed surface layer from the much colder deep-water layer.

Radiolarian oozes are siliceous pelagic sediments found in deep ocean basins. They typically occur at depths between 2000 and 5000 fathoms, where the dissolution of calcium carbonate allows these silica-based remains to accumulate.

High salinity is caused by high evaporation and low freshwater input. Anticyclonic conditions (high pressure and temperature) promote evaporation, while low precipitation ensures that the salt concentration remains high.

The average salinity of ocean water is approximately 35 parts per thousand, which is equivalent to 3.5 percent. This means that for every 1,000 grams of seawater, there are about 35 grams of dissolved salts. Salinity can vary slightly depending on evaporation rates and freshwater input from rivers.

An atoll is a ring-shaped coral reef, island, or series of islets that surrounds a body of water called a lagoon. They typically form when a coral reef grows around a volcanic island that eventually subsides or sinks beneath the ocean surface. Fringing reefs and barrier reefs are different structures that do not fully enclose a central lagoon in this circular fashion.

Approximately 71% of the Earth's surface is covered by water, primarily in the form of oceans. The remaining 29% consists of continents and islands. This high percentage of water is why Earth is often referred to as the 'Blue Planet'.