[Mission 2022] QUIZ – 2020: INSIGHTS STATIC QUIZ, 2 November 2021 – Geography

Solution: c)

• Dead Zone is an area in water body that contains little or no oxygen (or they are hypoxic) in bottom and near-bottom water.
• Mostly they occur naturally but it can be caused by excessive nutrient pollution from human activities coupled with other factors.
• They are well-known off western coasts of North and South America, off coast of Namibia and off west coast of India in Arabian Sea.
• In recent times, warming of the atmosphere through climate change is predicted to lead expansion of ‘dead zones’ in the ocean.

Solution: a)

• The oceans store much more carbon than the atmosphere and the terrestrial biosphere (plants and animals).
• The carbon, however, requires centuries to penetrate into the deep ocean, because the mixing of the oceans is a rather slow.
• However, even more carbon is stored in the lithosphere, i.e. the rocks on the planet, including limestones (calcium carbonate, CaCO3).

Solution: d)

• A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics.
• This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.
• The mid-ocean ridges of the world are connected and form a single global mid-oceanic ridge system that is part of every ocean, making the mid-oceanic ridge system the longest mountain range in the world, with a total length of about 60,000 km.
• It is characterised by a central rift system at the crest, a fractionated plateau and flank zone all along its length.
• The rift system at the crest is the zone of intense volcanic activity.

Solution: a)

Ocean vents eject hot, often toxic, fluids and gases into the surrounding seawater. They often mark sites of tectonic activity, and create some of the most hostile habitats on Earth.

Ocean vents are the product of tectonic activity beneath the ocean floor. Tectonic activity describes the way tectonic plates, giant slabs of Earth’s lithosphere, interact with each other.

Ocean vents are found in all ocean basins, although they are most abundant around the Pacific Ocean’s “Ring of Fire,” which also includes active earthquake zones, volcanoes, and ocean trenches.

Ocean vents are primarily found around mid-ocean ridges and volcanic arcs. At both mid-ocean ridges and back-arc basins, the molten magma of Earth’s asthenosphere wells up close to the surface.

Solution: d)

Ocean vents are a type of hydrothermal vent. Other types of hydrothermal vents include hot springs, geysers, and fumaroles. As their name indicates, all hydrothermal vents are characterized by water (hydro-) and extremely high temperatures (thermal).