Movements of Ocean Water 


EXERCISES

1. Multiple choice questions.

 (i) Upward and downward movement of ocean water is known as the :

(a) tide (c) wave

(b) current (d) none of the above

Ans: (a) tide.

 (ii) Spring tides are caused :

(a) As result of the moon and the sun pulling the earth gravitationally in the same direction.

(b) As result of the moon and the sun pulling the earth gravitationally

in the opposite direction.

(c) Indention in the coast line.

(d) None of the above.

Ans: (a) As result of the moon and the sun pulling the earth gravitationally in the same direction.

(iii) The distance between the earth and the moon is minimum when the moon is in :

(a) Aphelion (c) Perihelion

(b) Perigee (d) Apogee

Ans: (b) Perigee.

(iv) The earth reaches its perihelion in:

(a) October (c) July

(b) September (d) January

Ans: (d) January.


2. Answer the following questions in about 30 words.

(i) What are waves?

Ans: Imagine a ripple spreading across a pond – that's the essence of a wave! It's a disturbance that transfers energy through a medium (like water or air) without actually transporting the medium itself. They come in all shapes and sizes, from gentle ocean swells to crashing surf, sound waves vibrating molecules in the air, and even light waves rippling through space. Their movement and properties can be fascinating to explore! 


(ii) Where do waves in the ocean get their energy from?

Ans: Ocean waves catch a ride on various forces: wind's playful push, earthquakes' mighty shove, moon's gentle tug, and bottom's playful nudge. They're surfers of the sea, forever chasing energy!

(iii) What are tides?

Ans: Tides are the ocean's rhythmic breath, a rise and fall orchestrated by a moonlit tug-of-war. Earth's water bulges, swept by gravitational waves, creating highs and lows that paint our coasts a watery ballet. 

(iv) How are tides caused?

Ans: Earth and Moon, a cosmic dance! Their gravity pulls, water bulges, twice a day. Highs like peaks, lows like valleys, ocean's rhythmic ballet. Sun joins the waltz, stronger swells or gentle sway. Remember, tides are a celestial show!

(v) How are tides related to navigation?

Ans: High tides unlock harbors, charts guide the way, but hidden snags and tricky currents say: respect the ocean's watery sway. Navigators, allies and rivals in the tide's ballet!

3. Answer the following questions in about 150 words.

(i) How do currents affect the temperature? How does it affect the temperature of coastal areas in the N. W. Europe?

Ans: Currents act like giant conveyor belts in the ocean, transporting heat around the globe and influencing the temperature of coastal areas. Here's how:

Direct Temperature Impact:

*Warm Currents: Flowing from the tropics, warm currents like the Gulf Stream carry heat towards cooler regions, increasing the temperature of coastal areas they encounter. For example, in Northwest Europe, the Gulf Stream significantly warms the climate compared to similar latitudes, making winters milder and fostering lush vegetation. 

*Cold Currents: Conversely, cold currents like the Labrador Current bring up frigid water from the depths, lowering coastal temperatures. This can create stark contrasts, like the chillier climate of Newfoundland compared to England at similar latitudes. 

Indirect Temperature Impact:

*Moisture and Precipitation: Warm currents can influence regional precipitation patterns by transporting moisture and releasing it as rain or snow in coastal areas. For instance, the warm Kuroshio Current contributes to Japan's abundant rainfall.

*Fog and Cloud Formation: Cold currents can create foggy conditions or influence cloud formation near coasts, impacting sunlight received and potentially affecting local temperatures.

Northwest Europe Example:

    The Gulf Stream's influence on Northwest Europe is a prime example of how currents impact coastal temperatures. It brings warm tropical water from the Caribbean and Florida up the eastern coast of North America and across the Atlantic to Europe. This significantly warms the climate of countries like Ireland, England, and Norway compared to their latitudes, making them milder and wetter than they would be otherwise. Without the Gulf Stream, winters in Northwest Europe would be much colder and drier, potentially impacting ecosystems and agriculture.

    Understanding the influence of currents on temperature is crucial for various fields, from climate modeling and weather forecasting to fisheries management and coastal development. Studying these ocean highways reveals the intricate link between global ocean circulation and regional climates, highlighting the interconnectedness of our planet's systems.

(ii) What are the causes of currents?

Ans: The ocean's not just a still pond! Currents churn and flow, driven by several forces:

1. Wind: The main engine! Wind blowing across the water's surface drags on it, creating surface currents that flow in the direction of the wind. Imagine the wind like a hand brushing across the water, setting it in motion.

2. Density Differences: Water density can vary due to temperature and salinity. Warmer, less dense water rises, while colder, denser water sinks. These differences in density create vertical currents, driving deep-sea circulation. Think of it as warm water bubbling up and cold water sinking down.

3. Earth's Rotation: The Coriolis effect, caused by Earth's rotation, deflects currents to the right in the Northern Hemisphere and left in the Southern Hemisphere. This adds a twist to current patterns, shaping their paths and influencing their interactions.

4. Topography: The ocean floor isn't flat! Mountains, ridges, and trenches can guide and steer currents, causing them to speed up, slow down, or even change direction. Imagine currents navigating an underwater landscape.

5. Global Ocean Circulation: Driven by wind patterns and temperature differences, a vast network of currents circulates throughout the oceans, connecting different regions and transporting heat around the globe. It's like a planetary conveyor belt, constantly on the move.

    These forces work together to create the complex and dynamic dance of ocean currents, shaping marine ecosystems, influencing weather patterns, and even impacting global climate. Understanding these driving forces helps us appreciate the ocean's hidden engine and its profound influence on our planet.




Answer By: Himashree Bora.