Study Material Of GEO295 PDF

**Study material of GEO295** *UNIT 4* **The bottom topography of Indian Ocean is highly dynamic due to the interaction of tectonic plates, including the Indo-Australian Plate, African Plate, Eurasian Plate, and Antarctic Plate.** The Indian Ocean is one of the world's busiest maritime trade route...

**Study material of GEO295** *UNIT 4* **The bottom topography of Indian Ocean is highly dynamic due to the interaction of tectonic plates, including the Indo-Australian Plate, African Plate, Eurasian Plate, and Antarctic Plate.** The Indian Ocean is one of the world's busiest maritime trade routes, connecting major ports in Asia, the Middle East, Africa, and Europe. It is a critical corridor for global trade and commerce. The dynamic geological activity, along with its diverse marine life and unique ecosystems, makes the Indian Ocean a fascinating area for scientific research and exploration. **Indian Ocean** The Indian Ocean is the third-largest of the world's oceans, covering an area of approximately 27 million square miles (70 million square kilometres). - The coasts of Africa surround it to the west, Asia to the north, Australia to the east, and the southern Indian Oceanic islands to the south. - It is the only ocean that is named after a country (India). The Indian Ocean is surrounded by diverse coastlines, including the arid deserts of the Arabian Peninsula, the tropical rainforests of Southeast Asia, the savannas of eastern Africa, and the urbanized coasts of India and Australia. The Indian Ocean is known for the monsoon winds, which are seasonal wind patterns that influence the climate and weather in the region. The [Southwest Monsoon](https://www.clearias.com/mechanism-of-indian-monsoon/), in particular, brings heavy rainfall to the Indian subcontinent during the summer months. The Indian Ocean contains a rich and diverse marine ecosystem, with coral reefs, seagrass beds, and a wide variety of marine species, including whales, dolphins, sharks, and colorful reef fish. The Indian Ocean, like all major oceans, has a complex and varied bottom topography characterized by a combination of deep ocean basins, mid-ocean ridges, oceanic trenches, and seamounts. **Ocean Ridges** - The Mid-Indian Ridge is the prominent mid-ocean ridge that runs north-south through the central part of the Indian Ocean. - It is a divergent boundary where the African Plate and the Indo-Australian Plate are moving away from each other. - This ridge system is a significant geological feature, and it plays a role in the creation of new oceanic crust. **Deep Ocean Basins** - The Indian Ocean contains several deep ocean basins, including the Arabian, Somali, Mozambique, and Central Indian Basin. - These basins are characterized by their relatively flat and abyssal seafloor, with depths exceeding 4,000 meters (13,000 feet). **Oceanic Trenches** - The Sunda Trench, also known as the Java Trench, is one of the major oceanic trenches in the Indian Ocean. - It is located south of Java, Indonesia, and marks the subduction zone where the Indo-Australian Plate is descending beneath the Eurasian Plate. - In addition to the Sunda Trench, there are other deep-sea trenches in the Indian Ocean, such as the Diamantina Trench in the southeastern part of the ocean. - The Indian Ocean features numerous seamounts, underwater mountains, and guyots (flat-topped seamounts) scattered throughout its expanse. - These seamounts are often remnants of ancient volcanic activity and can rise thousands of meters from the ocean floor. **Island Chains and Archipelagos** - The Indian Ocean is home to several island chains and archipelagos, including the Maldives, Seychelles, and Chagos Archipelago. These volcanic and coral islands are often located on underwater ridges and plateaus. **Continental Shelves** - Around the periphery of the Indian Ocean, there are extensive continental shelves, particularly along the coasts of India, Indonesia, Australia, and East Africa. These shallow regions are the submerged extensions of the continents and are important for fisheries and oil and gas exploration. Advances in seafloor mapping and exploration have provided scientists with detailed insights into the Indian Ocean's bottom topography, helping to study its geological processes and marine ecosystems. **Bottom topography of Pacific Ocean** **The bottom topography of the Pacific Ocean is influenced by its tectonic activity, including subduction zones, mid-ocean ridges, and hotspot-related volcanic activity.** The diverse array of geological features contributes to the Pacific Ocean's unique biodiversity and plays a crucial role in shaping global ocean circulation patterns and climate dynamics. The Pacific Ocean serves as a vital route for international trade, with busy shipping lanes connecting Asia to the Americas and Oceania. The Pacific Ocean is the largest and deepest of Earth's oceans, covering more than 60 million square miles (about 165 million square kilometers) and accounting for more than one-third of the world's total ocean area. It is known for its immense size, diverse marine life, and critical role in global climate and weather patterns. - The Pacific Ocean is the largest of the world's five oceans, surpassing the combined size of all the Earth's landmasses. - It extends from the Arctic Ocean in the north to the Southern Ocean in the south and is bounded by the continents of Asia and Australia to the west and the Americas to the east.  The Pacific Ocean, the largest and deepest of the world's oceans, exhibits a complex and varied bottom topography. This topography includes deep trenches, seamounts, ridges, basins, and plateaus. **North Pacific Ocean** The North Pacific Ocean encompasses the area north of the equator and includes several subregions: - **Bering Sea:** Located between Alaska and Russia, the Bering Sea is known for its rich marine life and is an important fishing area. - **Sea of Japan (East Sea):** This semi-enclosed sea lies between Japan and the Korean Peninsula. - **North Pacific Subtropical Gyre:** This is a large system of rotating ocean currents in the subtropical North Pacific. The North Pacific High-pressure system dominates this region, resulting in relatively calm and dry conditions. - **Gulf of Alaska:** Situated between the southern coast of Alaska and the Aleutian Islands, this area is characterized by the convergence of cold, nutrient-rich waters from the north and warm currents from the south. **Central Pacific Ocean** The Central Pacific Ocean lies between the North and South Pacific and includes the following subregions: - **Hawaiian Islands:** This archipelago is one of the most famous in the world and is located in the central North Pacific. - **Equatorial Pacific:** This region near the equator includes the Line Islands and the Kiribati atolls. - **Marshall Islands and Federated States of Micronesia:** These island nations are located in the central and western equatorial Pacific. **South Pacific Ocean** The South Pacific Ocean includes a vast area of ocean south of the equator, comprising numerous island nations and territories: - **Polynesia:** This region includes islands such as Tahiti, Samoa, Tonga, and the Hawaiian Islands. It extends from Hawaii in the north to New Zealand in the south. - **Melanesia:** Encompassing islands like Papua New Guinea, Fiji, and the Solomon Islands, Melanesia is located to the west and southwest of Polynesia. - **Micronesia:** Situated in the western Pacific, Micronesia includes islands like Guam, the Northern Mariana Islands, and the Federated States of Micronesia. **Western Pacific Ocean** The Western Pacific Ocean is the region to the west of the International Date Line and includes: - **Philippine Sea:** An extension of the western Pacific, this sea is located between the Philippines and Taiwan. - **East China Sea:** Situated between China, Taiwan, and Japan, this sea is part of the northwestern Pacific Ocean. **Eastern Pacific Ocean** The Eastern Pacific Ocean includes the region off the western coast of the Americas, from North America to South America. - **California Current:** This is a cold ocean current that flows southward along the western coast of North America, influencing the climate and marine ecosystems of the region. - **Peru Current:** Also known as the Humboldt Current, this cold ocean current flows northward along the western coast of South America. **Trenches** - **Mariana Trench:** The Mariana Trench, located in the western Pacific, is the deepest part of the world's oceans. The trench reaches a maximum known depth of approximately 36,070 feet (10,994 meters) at a point called the Challenger Deep. It is the result of the subduction of the Pacific Plate beneath the Mariana Plate. - **Philippine Trench:** Situated to the east of the Philippines, this trench is another deep subduction zone in the western Pacific Ocean. - **Japan Trench:** Found off the eastern coast of Japan, the Japan Trench is a subduction zone created by the Pacific Plate diving beneath the North American Plate. It is associated with seismic activity and tsunamis. - **Tonga Trench:** Located in the southwestern Pacific, the Tonga Trench is another subduction zone where the Pacific Plate subducts beneath the Tonga Plate. - **Peru-Chile Trench:** Running along the western coast of South America, this trench is a subduction zone where the Nazca Plate is subducting beneath the South American Plate. **East Pacific Rise** - The East Pacific Rise is a mid-ocean ridge system that runs north-south along the eastern Pacific Ocean floor. - It is a divergent plate boundary where the Pacific Plate and the Nazca Plate are moving apart, leading to volcanic activity and the formation of new oceanic crust. - A minor ridge known as Galapagos Ridge runs parallel to the East Pacific Ridge in the east between the Eastern Island Fracture Zone and Galapagos is­lands. **Hawaii-Emperor Seamount Chain** - This seamount chain extends from the Hawaiian Islands in the northeast to the Emperor Seamounts in the northwest. - It is the result of the Pacific Plate moving over a hotspot, leading to the formation of volcanic islands and seamounts. *Distribution of Temperature and the Salinity in the Ocean* The Distribution of [**Temperature** ](https://en.wikipedia.org/wiki/Temperature)and salinity of oceans play crucial roles in various phenomena such as the **vertical** and **horizontal** circulation of ocean water, the movement of surface and **subsurface currents**, and the climate of different locations. These **factors** vary across the globe, resulting in diverse impacts on different regions.  **Average Temperature of Ocean water** - The sea surface typically has an **average temperature** of approximately **20°C (68°F),** although it can vary depending on the location.  - In **warm tropical regions**, the temperature can **exceed 30°C (86°F),** while at high latitudes, it can **drop below 0°C**. Generally, as you go deeper into the ocean, the water becomes colder. **Distribution of Temperature ** **How is temperature distributed throughout the ocean?** - The **temperature of the water** in the ocean plays a crucial role for marine organisms such as **phytoplankton** and **zooplankton.**  - It also has an impact on the climate of coastal areas and the plants and animals that inhabit them.  - **Thermometers** placed at different locations in the ocean are able to measure the temperature with an accuracy of approximately **±0.2° C**.  - In tropical regions, the ocean can be **divided into three layers** from the surface to the bottom. 1. The **initial layer** corresponds to **the uppermost layer of warm ocean water** and has a thickness of 500 meters. Its temperature ranges between 20° and 25°C.  2. The **thermocline layer** is a vertical zone of oceanic water located below the surface layer. It is distinguished by a significant decrease in temperature as depth increases. 3. The **third layer** of the ocean is characterized by extreme coldness and it stretches all the way down to the ocean floor.  Temperature Distribution Throughout the Ocean*Fig: Vertical distribution of the temperature* **Factors Affecting the Distribution of Temperature** - The Sun is the primary contributor to the temperature of ocean water. It emits radiant energy, known as **insolation**, in the form of shortwave electromagnetic waves from its photosphere.  ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ **Latitudes** -- The temperature of surface water decreases as you move from the **equator towards** the poles. This is due to the **Sun's rays becoming more slanted,** resulting in a **decrease in the amount of sunlight reaching the water in polar regions**. \ \ -- However, the poles in both hemispheres, the temperature of surface water becomes higher than the air temperature. -------------------------------------------------------------------- --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **Unequal Distribution of Land and Water** -- In the **northern hemisphere**, the oceans receive more heat because they come into contact with a larger **amount of land compared to the oceans **in the southern hemisphere. \ -- As a result, the surface water in the northern hemisphere tends to have a **higher temperature** than in the southern hemisphere. \ \ -- The isotherms in the **northern hemisphere are irregular** and do not follow latitudes due to the presence of both warm and cold land masses.  **Prevailing Wind** -- The **distribution of ocean water temperature** is significantly influenced by **wind direction**. \ \ -- When winds blow from the land towards the oceans and seas, they push warm surface water away from the coast, causing cold bottom water to rise up from below in a process called **upwelling.**      \ (**Note:** Upwelling is also another factor)\ \ -- This leads to a **longitudinal variation** in temperature as **warm water** is replaced by cold water. \ \ -- In contrast, when **onshore winds blow towards** the coast, they **cause warm water** to accumulate near the coast, resulting **in an increase** in temperature. [**Ocean Currents**](https://www.nextias.com/blog/ocean-currents/) -- Surface temperatures of the oceans are regulated by **warm and cold ocean currents. **\ \ -- Warm currents increase the temperature in the regions they pass through, while cold currents decrease the temperature. \ \ -- For instance, the **North Atlantic Current (warm)** and (Labrador cold). ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ - This energy is **received at the surface of the ocean**. Additionally, some **energy is received** from below the **ocean's bottom** and through the compression of seawater. **Horizontal and Vertical Distribution of Temperature** **Horizontal Distribution of Temperature** - On average, **the surface water temperature** of the oceans is 26. °C (80°F), gradually decreasing from the **equator towards the poles**.  - In the northern hemisphere, the **oceans tend** to have a higher average temperature compared to the southern hemisphere.  - This **temperature variation between the hemispheres is due to the unequal distribution of land and ocean water. ** - The **average annual temperature** of the **Pacific Ocean** is slightly higher than that of the **Atlantic Ocean** (16. 1 °C or 60°F) and the **Indian Ocean** (17°C or 60. °F).  - Additionally, the surface water temperature of the oceans is higher than the air temperature above the ocean surface, indicating that the ocean surface releases heat to the [**atmosphere**](https://www.nextias.com/blog/earths-atmosphere/). [**Vertical Distribution of Temperature**](https://www.nextias.com/current-affairs/26-04-2023/understanding-temperature-anomalies/) - The **maximum temperature** of the oceans is consistently found at their surface because **it directly absorbs sunlight**, and the heat is then transferred to the deeper layers of the oceans through conduction.  - Sunlight is able to penetrate up to a **depth of 20 meters** in the ocean and rarely goes beyond 200 meters.  - The **upper surface of the ocean**, known as the **Photic or Euphotic zone**, extends up to a depth of 200 meters and is where [**solar radiation**](https://www.nextias.com/blog/solar-radiation/) is received. **The General Distribution of Salinity in the Ocean** **Salinity of Ocean Water** - The **salinity of sea water** refers to the overall weight of dissolved salts in one kilogram of sea water.  - Salinity is measured in **units of g/kg**, often denoted as p.p.t. (Parts per thousand) or ‰ (per mil).  - On average, **sea water contains approximately 3½ percent salt**, meaning that every 1,000 grams of sea water contains nearly 35 grams of salt.  - Out of the **total salt content**, **sea water** consists of about 77 percent **sodium chloride** or **common salt**. **Factors Affecting Distribution of Salinity of Ocean Water** -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **Evaporation** -- There is a **direct correlation** between the **rate of evaporation** and **salinity**. \ \ -- or, **when evaporation is higher**, **salinity** also tends to be **higher**, and **vice versa**. \ \ -- For instance, **areas near the tropics** have higher salinity compared **to the equator due to the high rate of evaporation** in these regions. \ \ -- This is particularly true when dry air is present over the tropics of Cancer and Capricorn. --------------------------------------------- ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **Precipitation** -- **Precipitation** and **salinity** have an inverse relationship. \ \ -- In other words, **when precipitation is high, salinity is low, and vice versa.** \ \ -- This is why **areas with high rainfall**, like the **equatorial zone**, tend to have lower salinity compared to **regions with low rainfall**, such as the **sub-tropical high pressure belts**.  **Influx of river water** -- The rivers transport salt from the land to the oceans. However, when **large and voluminous rivers** flow into the oceans, they bring a significant amount of water, which leads to a reduction in salinity at their mouths.  **Atmospheric Pressure and Wind Direction** -- The salinity of the ocean's surface water rises under anticyclone conditions of **stable air and high temperature**. \ \ -- High pressure zones in the subtropics are examples of these circumstances. \ \ -- Winds also aid in the redistribution of salt in the **oceans** and **by** driving salty water to less salty places, which causes the former to become less salty and the latter to become saltier.\ \ -- These areas are known as **upwelling regions** because they see the replacement of saline surface water with substantially less saline subsurface water. **Impact of Ocean Currents** -- Through the **mixing of seawaters**, **ocean currents** influence the regional distribution of salinity. \ \ -- Warm equatorial currents transport salt away from the continents' western coasts and collect it along their eastern coastlines. -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- **Horizontal Distribution of Salinity** **Higher Salinity Near Tropic of Cancer and Tropic of Capricorn** - The temperature near the **tropics of Cancer** and **Capricorn** is very high. Here, **evaporation is very high** near the tropics because **the sky is usually clear** and the oceans are exposed to the onshore trade winds. This causes concentration of salts. - Hence salinity of seas and oceans in these regions is very high.  **Lower Salinity in Equatorial Regions** - In the **equatorial region**, the salinity is comparatively low due to the **higher amount of rainfall**. And this region is impacted by **various large rivers** that bring **fresh water** into the ocean.  - Consequently, the combination of **increased rainfall**, higher relative humidity, cloud cover, and the influx of fresh water prevents significant evaporation, resulting in lower salinity levels.  **Lowest Salinity in Poleward Region** - Towards pole the **salinity decreases **because of low evaporation and low temperature. In addition to this, the melting of ice provides the fresh water which leads to decrease the salinity in the polar region.  **Vertical Distribution of Salinity** **Salinity Increases with Increasing Depth** - Salinity tends to **rise as the depth increases** in high latitudes.  - However, in middle latitudes, this trend is limited to a **depth of 200 fathoms** from the surface, after which salinity decreases with increasing depth.  - At the equator, the **surface salinity** is **low due to high rainfall** and the movement of water through equatorial currents.  - However, beneath the surface, higher salinity levels are observed.  **Ocean Deposits** **Ocean Deposits** An ocean deposit is a natural buildup of solid, liquid, or gas found on the Earth's surface, in its waters, or in the atmosphere. These deposits are also called marine deposits, and the process of forming them is known as marine deposition. An ocean deposit is a naturally occurring accumulation of solid, liquid, or gaseous material on the earth's surface, within its waters, or within its atmosphere. Ocean deposits are also known as marine deposits. A marine deposition is a process where these materials are deposited. **Ocean Deposit Types** Ocean deposits can be classified on the basis of different criteria including location, depth, sediments, etc. **Based on Location** **Shelf Deposits: ** These are deposits that are found on the continental shelf, which is the shallowest part of the ocean. Shelf deposits can further be classified into four types: **Terrigenous Deposits:** These are deposits that are formed from materials that have been transported to the ocean by rivers, wind, or glaciers. **Biogenous Deposits:** These are deposits that are formed from the remains of marine organisms. **Hydrogenous Deposits:** These are deposits that are formed when minerals precipitate out of a solution in the water. **Cosmogenic Deposits:** These are deposits that are formed by the action of cosmic rays on the ocean floor. **Based on Depth** **Continental Shelf Deposits: ** These are deposits that are found on the continental shelf, which is the shallowest part of the ocean. **Continental Slope Deposits:** These are deposits that are found on the continental slope, which is the steepest part of the ocean. **Oceanic Basin Deposits:** These are deposits that are found in the oceanic basin, which is the deepest part of the ocean. **Based on Sediments** **Clastic Deposits:** These are deposits that are composed of particles of rock or sediment that have been transported to the ocean by rivers, wind, or glaciers. **Non-clastic Deposits:** These are deposits that are not composed of particles of rock or sediment, but are instead composed of minerals that have precipitated out of solution in the water. Ocean deposits can also be classified on the basis of their origin, which can be either natural or man-made. Hence it can be said that ocean deposits can be classified on the basis of different criteria including location, depth, sediments, origin, etc. **Importance of Ocean Deposit** Ocean deposits are important because they: - Provide information on the history of the ocean - Can be used to study changes in ocean currents - Can be used to study the ocean floor - Provide information on past climates - Can be used to study the ocean's role in the carbon cycle - Can be used to study the ocean's role in the global water cycle Ocean deposits are important for several factors as mentioned above. They give us an insight into the happenings of the ocean and how it has changed over time. It also helps in the study of oceanography which is the study of the ocean. Oceanography is a branch of earth science that deals with the physical and chemical properties of the ocean and its interaction with the atmosphere, lithosphere, and hydrosphere. It covers a wide range of topics from plate tectonics and ocean currents to marine life and oceanography. Ocean deposits are also important for the study of climate change. Climate change is one of the most pressing issues facing our planet today. The ocean plays a vital role in regulating the Earth's climate. Ocean deposits can give us clues about how the ocean has responded to past climates and the coming climate changes. **Ocean Deposit: Examples** Ocean deposit examples are classified according to their mineralogy, chemistry and texture. The main examples of ocean deposits are: **Rocks:** Oceanic crust is made up of rocks such as basalt, gabbro and granite. **Minerals:** Ocean deposits also include minerals such as olivine, pyroxene and amphibole. **Sediments:** Ocean sediments include clay, sand and gravel. **Organisms:** Ocean organisms such as plankton, algae and corals can also be considered ocean deposits. **Conclusion** it is important to have a clear understanding of the concept of ocean deposit in order to make informed decisions about our use of the world's oceans. Ocean deposits are a key part of the Earth's geology and play a vital role in many aspects of our lives, from the food we eat to the water we drink. With a better understanding of ocean deposits, we can make more informed choices about how we use and conserve our environment. Ocean deposit types can be classified according to their formation process. In this article, we talk about the meaning of ocean deposit, ocean deposit types and ocean deposit examples. Ocean Currents It is a horizontal movement of seawater that is produced by gravity, wind, and water density. Ocean currents play an important role in the determination of climates of coastal regions. **Ocean Water and Ocean Currents** The movement of ocean water is continuous. This movement of ocean water is broadly categorized into three types: - Waves - Tides - Currents The streams of water that flow constantly on the ocean surface in definite directions are called ocean currents. Ocean currents are one of the factors that affect the temperature of ocean water. - Warm ocean currents raise the temperature in cold areas - Cold ocean currents decrease the temperature in warmer areas. What are Ocean Currents? - Ocean currents are the continuous, predictable, directional movement of seawater. It is a massive movement of ocean water that is caused and influenced by various forces. They are like river flows in oceans. - Ocean water moves in two directions: horizontally and vertically. - Horizontal movements are referred to as currents, while vertical changes are called upwellings or down wellings. - Ocean currents impact humankind and the biosphere due to their influence on climate. Which are the Factors that Influences Ocean Current? - Ocean currents are influenced by two types of forces namely: - **Primary forces:** - **Heating by solar energy:** Heating by solar energy causes the water to expand. That is why, near the equator the ocean water is about 8 cm higher in level than in the middle latitudes. This causes a very slight gradient and water tends to flow down the slope. - **Wind**: Wind blowing on the surface of the ocean pushes the water to move. Friction between the wind and the water surface affects the movement of the water body in its course. - **Gravity:** Gravity tends to pull the water down the pile and create gradient variation. - **Coriolis force**. The Coriolis force intervenes and causes the water to move to the right in the northern hemisphere and to the left in the southern hemisphere. - These large accumulations of water and the flow around them are called Gyres. - These produce large circular currents in all the ocean basins. - **Secondary forces:** - **Differences in water density:** It affects vertical mobility of ocean currents. - Water with high salinity is denser than water with low salinity and in the same way cold water is denser than warm water. - Denser water tends to sink, while relatively lighter water tends to rise. - **Temperature of water:** Cold-water ocean currents occur when the cold water at the poles sinks and slowly moves towards the equator. - Warm-water currents travel out from the equator along the surface, flowing towards the poles to replace the sinking cold water. **What are the Types of Ocean Currents?** - The ocean currents may be classified based on their depth: - **Surface currents:** Large-scale surface ocean currents are driven by global wind systems that are fueled by energy from the sun. - These currents transfer heat from the tropics to the polar regions, influencing local and global climate. - It constitute about 10% of all the water in the ocean, these waters are the upper 400 m of the ocean. - **Deep water currents:** Differences in water density, **resulting from the variability of water temperature (thermo)** and **salinity (haline)**, also cause ocean currents. This process is known as thermohaline circulation. - It makes up the other 90% of the ocean water. - These waters move around the ocean basins due to variations in the density and gravity. - Deep waters sink into the deep ocean basins at high latitudes, where the temperatures are cold enough to cause the density to increase. - This starts\' the **global conveyor belt**, a connected system of deep and surface currents that circulate around the globe on a 1000 year time span. - This global set of ocean currents is a critical part of Earth's climate system as well as the ocean nutrient and carbon dioxide cycles. - Ocean currents can also be classified based on temperature: - **Cold currents**: It brings cold water into warm water areas. These currents are usually found on the west coast of the continents in the low and middle latitudes (true in both hemispheres) and on the east coast in the higher latitudes in the Northern Hemisphere. - **Warm currents**: It brings warm water into cold water areas and is usually observed on the east coast of continents in the low and middle latitudes (true in both hemispheres). - In the northern hemisphere they are found on the west coasts of continents in high latitudes.  **What are the Characteristics of Ocean Currents?** - Major ocean currents are greatly **influenced by the stresses exerted by the prevailing winds and coriolis** **force.** The oceanic circulation pattern roughly corresponds to the earth's atmospheric circulation pattern. - The air circulation over the oceans in the **middle latitudes is mainly anticyclonic** (more pronounced in the southern hemisphere than in the northern hemisphere). The oceanic circulation pattern also corresponds with the same. - At** higher latitudes**, where the **wind flow is mostly cyclonic**, the oceanic circulation follows this pattern. - In regions of pronounced monsoonal flow, the **monsoon winds influence the current movements.** - **Due to the coriolis force,** the **warm currents from low latitudes tend to move to the right in the northern hemisphere **and to** their left in the southern hemisphere.** - The oceanic circulation **transports heat from one latitude belt to another** in a manner similar to the heat transported by the general circulation of the atmosphere. - The **cold waters of the Arctic and Antarctic circles move towards warmer water in tropical and equatorial regions, **while the** warm waters of the lower latitudes move polewards.** **What are the Various Ocean Currents?** - **Equatorial Currents System**: Every ocean, except the Arctic Ocean, has a North Equatorial Current, a South Equatorial Current and an Equatorial Counter Current. - The North and South equatorial currents flow from east to west. - **Equatorial Counter Current**: It is located between the North and South equatorial currents and flows in opposition to them, that is, from west to east. - **Antarctic Circumpolar Current (ACC):** The ACC is an ocean current that flows clockwise from west to east around Antarctica. An alternative name for the ACC is the West Wind Drift. - **Humboldt or Peruvian Current:** This low-salinity current has a large marine ecosystem and serves as one of the major nutrient systems of the world. - Flows from the southernmost tip of Chile to northern Peru, along the west coast of South America. - **Kurile or Oyashio Current**: This sub-arctic ocean current circulates in a counterclockwise direction. - It originates in the Arctic Ocean flows south via the Bering Sea in the western North Pacific Ocean. - It is a nutrient-rich current. - It collides with Kurioshio off the Japanese eastern shore to form the North Pacific Drift. - **California Current:** It is the extension of the Aleutian Current along the west coast of North America in a southward flowing direction. - It is a part of North Pacific Gyre. - Region of strong Upwelling. - **Labrador Current:** It flows from the Arctic Ocean towards the south and meets the warm northward moving Gulf Stream. - The combination of cold Labrador Current and warm Gulf Stream is known for creating one of the richest fishing grounds of the world. - **Canary Current:** Low salinity current extending between Fram Strait and Cape Farewell. - It connects the Arctic directly to the North Atlantic. - Major freshwater sink for the Arctic. - It is a major contributor to sea-ice export out of the Arctic. - **Benguela Current:** Branch of West Wind Drift of the Southern Hemisphere. - Eastern portion of South Atlantic Ocean Gyre. - Low salinity, presence of upwelling- excellent fishing zone. - **Falkland Current:** It is a branch of Antarctic Circumpolar Current. - It is also known as Malvinas Current. - It is named after the Falkland Islands. - This cold current mixes with warm Brazil current and forms the Brazil-Malvinas Confluence Zone which is responsible for the region's temperate climate. - **Northeast Monsoon Current:** Indian North Equatorial Current flows southwest and west, crossing the Equator. - **Somali Current:** Analogous to the Gulf Stream in the Atlantic Ocean. - The Current is heavily influenced by monsoon. - Region of major upwelling system. - **Western Australian Current:** It is also known as West Wind Drift. - It is a part of the Antarctic Circumpolar Current. - It is a seasonal current- strong in summer and weak in winter.' - **Kuroshio Current:** This west boundary current is also known as Japan current or Black Current. The term** "Kuroshio" in Japanese means "Black Stream \'\'.** - It is the Pacific analogue of the Gulf Stream in the Atlantic Ocean. - The average surface temperature of this current is warmer than the surrounding ocean. - This also helps in regulating the temperature of Japan, which is relatively warmer. - **North Pacific Current:** It is formed by the collision of Kurioshio & Oyashio. - It circulates counterclockwise along the Western North Pacific Ocean. - **Alaskan Current:** It results from a northward diversion of a part of the North Pacific Ocean. - **East Australian Current:** Acts to transport tropical marine fauna to habitats in sub-tropical regions along the southeast Australian coast. - **Florida Current:** Flows around Florida Peninsula and joins the Gulf Stream at Cape Hatteras. - **Gulf Stream**: Western intensified current-driven mainly by wind stress. - It splits into North Atlantic Drift (crossing Northern Europe & southern stream) and Canary Current (recirculating of West Africa) - **Norwegian Current:** This wedge-shaped current is one of the two dominant Arctic inflows of water. - It is a branch of North Atlantic Drift and sometimes also considered as an extension of the Gulf Stream. - **Brazilian Current:** Flows along the south coast of Brazil till Rio de la Palta. - It joins the cold Falkland Current at the Argentine Sea making it a temperate sea. - **Mozambique Current:** Flows between Mozambique and the island of Madagascar along the African east coast in the Mozambique Channel. - **Agulhas Current:** Largest western boundary ocean current. - Flows south along the east coast of Africa. - **Southwest Monsoon Current:** It dominates the Indian Ocean during the southwest monsoon season (June--October). - It is a broad eastward flowing ocean current that extends into the Arabian Sea and Bay of Bengal. **What are the Effects of Ocean Currents?** - **Climatic Conditions:** Currents influence the climatic conditions of the regions in which they flow. - The warm Equatorial currents raise the temperature of the region in which they flow. Similarly, the cold currents lower the temperature of the places where they flow. - For example, the British Isles would have been extremely cold without the warm North Atlantic Drift. - The hot climate of Peru is cooled by the cold Peru Current. - **Rainfall:** The winds blowing over warm currents pick up and carry moisture and bring rainfall like the North Atlantic Drift brings rainfall in some areas located along the western coasts of Europe. - On the contrary, cold currents do not bring rainfall and make the region cooler and drier. - The Kalahari Desert hardly experiences rainfall due to the cold Benguela current. - **Fog Formation:** The meeting of the warm and the cool currents results in the formation of fog. - The ship\'s face danger due to the fogs caused by the meeting of the warm currents with the cold currents. - This has resulted in the wreckage of many ships in the past as they are not able to view icebergs due to poor visibility. - **Creates Fishing Zone:** The mixing of warm and cold currents results in the deposition of planktons. Therefore, at such places, fishes can be found in abundance. - **Desert formation:** Cold ocean currents have a direct effect on desert formation in west coast regions of the tropical and subtropical continents. - There is fog and most of the areas are arid due to** desiccating effects** (loss of moisture). - **Trade and Commerce:** Currents help ships to sail if they follow the directions of the currents. - Many warm currents keep the ports of Europe ice free even during the winters. This helps in trade and commerce. - **Violent Storms:** At times the meeting line of a warm and a cold current may result in a violent storm. - The hurricanes which occur off the coast of the U.S.A. follow the line where the Gulf Stream merges with the Labrador Current. **Marine Resources** - **Marine resources**are materials and attributes found in the ocean that are considered to have value. That value can be intrinsic, or monetary. - They include a huge number of things: biological diversity, fish and seafood supplies, oil and gas, minerals, sand and gravel, renewable energy resources, tourism potential, and unique ecosystems like coral reefs. - These resources can have great monetary value, and even when they don't, the uniqueness and opportunity for education and human enrichment cannot be quantified. - The way we manage and use these resources is therefore of great importance. **Broad Classification of Ocean Resources** - **Biotic Resources: **The oceans' biological resources include f**ish, crabs, mollusks, coral, reptiles, and mammals,** among others.  1. **Planktons: **Zooplanktons and phytoplankton are microscopic organisms that float to the surface of the water.The microscopic **foraminifera, radiolarians, diatoms, coccolithophores, dinoflagellates, and larvae of several marine animals, such as fish, crabs, sea stars**, etc., are a few examples of planktons. 2. **Nekton:  **The animals that are actively moving in the water are considered nekton. Examples include invertebrates like **shrimp and vertebrates like fish, whales, turtles, and sharks.** 3. **Benthos: **The organisms that make up the benthos are those that are biologically connected to the ocean floor.** Echinoderms, crustaceans, mollusks, poriferans, and annelids** make up the majority of the benthos**.** **Abiotic Resources: ** - Abiotic resources of the ocean refer to non-living natural resources that can be found within the marine environment.  - They are broadly classified as **mineral resources and energy resources.** **Mineral resources: ** 1. **Minerals dissolved in seawater:  **Certain minerals are present in small quantities within seawater itself and can be extracted using specialized processes.  - **Continental Shelf and Slope Deposits: **These deposits are found on the shallow seabed regions, primarily on the continental shelves and slopes. For Examples**:** **Diamond, Fisheries Sector, Pearls, Monazite sand, a source of thorium, found off the Kerala coast**. 2. **Sediments on the deep ocean floor: **Nodules of manganese contain a variety of minerals, including lead, zinc, nickel, copper, cobalt, and copper. **Energy Reserves:** +-----------------------------------+-----------------------------------+ | **Wave Energy: ** | - When electrical generators | | | are positioned on the ocean's | | | surface, waves are created. | | | The desalination facilities, | | | power plants, and water pumps | | | consume the energy most | | | frequently. Wave height, wave | | | speed, wavelength, and water | | | density all affect energy | | | output. | | | | | | - It is believed that wave | | | energy has a t**heoretical | | | maximum capacity of over | | | 40,000 MW**. However, this | | | energy is not as potent as | | | that found at higher or lower | | | latitudes. | +===================================+===================================+ | **Tidal Energy: ** | - Tidal energy generators are | | | used to produce tidal energy. | | | | | | - High tidal zones are home to | | | massive underwater turbines | | | that are built to harness the | | | kinetic energy of the ocean | | | tides in order to generate | | | electricity. | | | | | | - The **Khambat and | | | Kutch **regions have | | | potential sites with a total | | | estimated potential | | | for **tidal energy of 12455 | | | MW.** | +-----------------------------------+-----------------------------------+ | **Ocean thermal energy conversion | - **Ocean thermal energy | | (OTEC): ** | conversion (OTEC)** runs a | | | heat engine and generates | | | usable work, typically in the | | | form of electricity, by | | | utilising the temperature | | | differential between **cooler | | | deep and warmer shallow or | | | surface seawaters.** | | | | | | - Its economic viability is | | | difficult because to the low | | | thermal efficiency caused by | | | the minor temperature | | | difference**.** | | | | | | - - **If appropriate | | | technology advancement | | | occurs, OTEC in India has a | | | theoretical capacity of | | | 180,000 MW.** | +-----------------------------------+-----------------------------------+ | **Offshore wind energy: ** | - Building wind farms on | | | waterways to harness the | | | power of the wind is known as | | | offshore wind power or | | | offshore wind energy. Since | | | offshore wind power | | | contributes more to the | | | supply of electricity than | | | wind power on land due to the | | | stronger wind speeds that are | | | available there. | | | | | | - **India's 7,600 | | | kilometer-wide coastline has | | | the potential to generate | | | approximately 140 Gigawatt | | | (GW) of electricity from | | | offshore wind.** | +-----------------------------------+-----------------------------------+ | **Natural Gas: ** | - Shale gas, tight gas, and | | | occasionally unconventional | | | natural gas are terms used to | | | describe natural gas. | | | Additionally, natural gas can | | | be found in crude oil | | | deposits; Natural gas | | | resources can be | | | discovered** offshore and | | | deep beneath the ocean's | | | surface, as well as on | | | land.** | | | | | | - **India has 541 BCM of | | | economically viable natural | | | gas deposits (on land, in | | | Assam and Gujarat), plus 190 | | | BCM more offshore in the Gulf | | | of Cambay and 190 BCM in the | | | Bombay High. Recently, a | | | sizable 400 BCM deposit was | | | discovered in the Tripura | | | Basin.** | +-----------------------------------+-----------------------------------+ | **Clathrate Hydrates: ** | - Clathrate hydrates, also | | | known as gas hydrates, | | | clathrates, or hydrates, are | | | crystalline water-based | | | solids that have a | | | consistency similar to ice | | | and contain small non-polar | | | molecules or polar molecules | | | with significant hydrophobic | | | moiety trapped inside 'cages' | | | of frozen, hydrogen-bonded | | | water molecules.  | | | | | | - India's **1,894 trillion | | | cubic meters of gas hydrate | | | resources** are located | | | in **Western, Eastern, and | | | Andaman offshore areas. ** | | | | | | - Two promising sites | | | in **Krishna-Godavari and | | | Mahanadi basins** and large | | | enriched **gas hydrate | | | reserves in Bay of Bengal.** | +-----------------------------------+-----------------------------------+ **Blue economy:** - As per the World Bank, the blue economy is defined as "**sustainable use of ocean resources for economic growth, improved livelihoods, and jobs while preserving the health of the ecosystem."** - The blue economy comprises a range of economic sectors and related policies that together determine whether the use of ocean resources is sustainable.  **Components of Blue economy:** - **Fisheries and Aquaculture:** Sustainable fishing practices and responsible aquaculture contribute to food security, employment, and income generation. - **Maritime Transportation and Shipping:** The shipping industry plays a crucial role in global trade and connectivity. - **Tourism and Recreation:** Coastal and marine tourism can stimulate local economies if  overexploitation and environmental degradation are avoided.. - **Renewable Energy:** The blue economy includes the development of renewable energy sources like offshore wind, wave, and tidal energy, reducing dependence on fossil fuels. - **Coastal Development:** Sustainable development of coastal areas involves balancing human activities with conservation efforts to protect marine ecosystems. **Challenges of blue economy:** - **Overfishing:** Fish population is being depleted faster than the rate of replenishment. This not only disrupts marine ecosystems but also impacts the livelihoods of coastal communities reliant on fishing. - **Pollution and marine debris:** Pollution from industrial waste, agricultural runoff, plastic debris, and oil spills adversely affect marine life, degrade habitats, and disrupt the entire marine food chain. - **Climate change impacts:** Rising ocean temperatures, sea level rise, and ocean acidification due to climate change pose serious threats to marine ecosystems and coastal communities. Coral bleaching, habitat loss, and shifts in species distribution negatively impact fishing and tourism industries. - **Illegal, unreported, and unregulated (IUU) fishing:** IUU fishing undermines sustainable fisheries management by bypassing regulations and quotas, posing risks to fish stocks and the livelihoods of legitimate fishers. - **Sustainable Technologies: **Developing sustainable technologies for ocean exploration and resource extraction is expensive and risky. Striking a balance between innovation and environmental concerns is essential for the blue economy's success. - **Limited technology and infrastructure: **Many coastal and developing regions lack the necessary technology and infrastructure to fully capitalize on blue economy opportunities, such as adequate port facilities, maritime transportation, and monitoring systems for sustainable resource management. - **Inadequate data and information:** Sound decision-making in the blue economy relies on accurate and up-to-date data on ocean resources and ecosystems. Gaps in data hinder the formulation of effective policies and strategies. - **Coastal erosion and habitat loss:** Human activities like coastal development and dredging contribute to habitat loss and erosion, severely impacting critical marine ecosystems like mangroves, salt marshes, and coral reefs. - **Collaboration among nations:** The sustainable management of ocean resources will require collaboration across borders and sectors through a variety of partnerships which is particularly challenging for Small Island Developing States (SIDS) and Least Developed Countries (LDCs) who face significant limitations.