Chapter 14 – Movements of Ocean Water
- What are the major movements of ocean water?
Ocean water moves in the form of waves, tides, and currents. These movements are driven by wind, gravity, the Moon and Sun’s gravitational pull, and Earth’s rotation. - What causes ocean waves?
Waves are generated mainly by wind blowing across the surface. Wind speed, duration, and fetch determine wave height, length, and frequency. - What is wave crest and trough?
The crest is the highest point of a wave, and the trough is the lowest point. The vertical distance between them is called wave height. - What is wavelength and wave height?
Wavelength is the horizontal distance between two crests or troughs. Wave height is the vertical distance between the crest and trough. - What is the period of a wave?
It is the time taken for two successive wave crests to pass a fixed point. It helps measure wave speed and energy. - What is swash and backwash?
Swash is the forward movement of water on a beach after a wave breaks. Backwash is the return flow of water back to the sea. - What are tides?
Tides are periodic rises and falls in sea level caused by the gravitational pull of the Moon and Sun, and the rotation of Earth. - What is a tidal range?
It is the vertical difference between the high tide and the low tide. It varies with the position of the Moon and coastline shape. - What are spring tides?
Spring tides occur during full and new moons when the Sun, Moon, and Earth align. This alignment increases gravitational force, creating higher high tides. - What are neap tides?
Neap tides occur during the first and third quarters of the moon when Sun and Moon are at right angles, resulting in weaker tides. - What are ocean currents?
Large-scale horizontal movements of ocean water in definite directions. They are driven by wind, Earth’s rotation, and differences in temperature and salinity. - What are surface currents?
Surface currents flow in the upper 400 meters of the ocean and are primarily driven by prevailing winds and Earth’s rotation (Coriolis force). - What is the Coriolis effect on ocean currents?
It deflects currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, influencing their direction globally. - What are gyres?
Gyres are large circular ocean current systems formed by wind and Coriolis force. There are five major gyres, like the North Atlantic and South Pacific. - What is the Gulf Stream?
A powerful warm Atlantic ocean current that originates in the Gulf of Mexico and flows towards Europe, significantly warming its western coastal regions. - What is the Labrador Current?
A cold current flowing south from the Arctic along the eastern coast of Canada. It cools the region and affects the fishing industry. - How do warm currents affect climate?
Warm currents raise temperatures of coastal regions and increase evaporation, often leading to more rainfall and a warmer climate. - How do cold currents affect climate?
Cold currents reduce coastal temperatures and often lead to dry climates by cooling air and suppressing rainfall. - What is upwelling?
An upward movement of cold, nutrient-rich water from the ocean depths to the surface, supporting marine productivity and fisheries. - What is downwelling?
The sinking of surface water into deeper layers, often due to convergence or cooling. It transports oxygen to deeper ocean layers. - What is thermohaline circulation?
A global ocean circulation driven by differences in temperature (thermo) and salinity (haline), also known as the “global conveyor belt.” - What is the global conveyor belt?
A deep-ocean circulation system moving water around the globe, driven by thermohaline forces. It distributes heat and regulates Earth’s climate. - What is the Humboldt Current?
A cold ocean current flowing northward along the west coast of South America. It supports one of the richest fishing grounds on Earth. - What is El Niño?
An irregular warming of eastern Pacific waters, disrupting normal ocean currents and weather patterns globally. It causes floods, droughts, and weakens monsoons. - What is La Niña?
A counterpart to El Niño, it involves unusually cold Pacific waters and strengthens trade winds, leading to more rainfall in India and colder global conditions. - What are subsurface currents?
These are ocean currents that occur below the surface, driven by density differences caused by salinity and temperature gradients. - What is the significance of ocean currents?
They regulate global climate, influence marine biodiversity, impact weather, and play a crucial role in maritime navigation and nutrient distribution. - How do ocean currents affect navigation?
Currents assist or hinder ships depending on their direction. Warm currents like the Gulf Stream speed up Atlantic crossings; cold ones may slow or endanger vessels. - What is tidal energy?
Tidal energy is renewable energy generated from the rise and fall of tides using turbines or barrages. It’s predictable but location-dependent. - Why are tides important?
They help in navigation, fishing, and generating energy. Tides also cleanse coastal areas by removing waste and circulating nutrients.