1. Consider the following factors: (1) Submarine earthquake (2) Underwater landslide (3) Volcanic eruption (4) Impact of meteorite on ocean floor Which of the above factors can trigger the tsunamis in the ocean? (a) 1 and 2 only (b) 1 and 3 only (c) 1, 2 and 3 only (d) 1, 2, 3 and 4
Answer: (d) Explanation: Tsunami, (Japanese: “harbour wave”), also called as seismic sea wave, is a catastrophic ocean wave, usually caused by a submarine earthquake, an underwater or coastal landslide, or a volcanic eruption. It can also occur due to the impact of meteorite(s). The term tidal wave is frequently used for such a wave, but it is a misnomer, for the wave has no connection with the tides. When an earthquake occurs; a train of simple, progressive oscillatory waves travels a great distance over the ocean surface in ever-widening circles. In deep water, a tsunami can travel as fast as 800 km (500 miles) per hour. The wavelengths are enormous, about 100 to 200 km (60 to 120 miles), but the wave amplitudes (heights) are very small, only about 30 to 60 cm (1 to 2 feet). The waves’ periods (the lengths of time for successive crests or troughs to pass a single point) are very long, varying from five minutes to more than an hour. These long periods, coupled with the extremely low steepness and height of the waves, enables them to be completely obscured in deep water by normal wind waves and swell. A ship in the high seas experiences the passage of a tsunami as an insignificant rise and fall of only half a metre (1.6 feet), lasting from five minutes to an hour or more. As the waves approach shoreline and enter shallower water they slow down and begin to grow in energy and height. The tops of the waves move faster than their bottoms do, which causes them to rise precipitously. Coastal waters may rise as high as 30 metres (about 100 feet) above normal sea level in 10 to 15 minutes. The continental shelf waters begin to oscillate after the rise in sea level. Between three and five major oscillations generate most of the damage. Oscillations may continue for several days until the ocean surface reaches equilibrium. 2. Match List-I with List-II and select the correct answer using the code given below the lists: List - I (Volcanic type) : List - II (Feature) A. Shield volcanoes : 1. Lava pit B. Cinder Cones : 2. Violent explosion C. Lava dome : 3. Highly viscous lava D. Caldera : 4. Gently rising slope with flat domes Codes A B C D (a) 2 1 4 3 (b) 2 4 3 1 (c) 4 2 3 1 (d) 1 2 3 4 Answer: (c) Explanation: A volcano is an opening in the Earth’s surface where molten rock can escape from underneath. The Earth’s surface is made up of tectonic plates, which are spreading apart, crunching into each other, or sliding beside one another. Volcanoes are typically found at the fault lines between these plates. Some important volcanic landforms: Shield volcanoes are large, broad volcanoes that look like shields from above – hence the name. The lava that pours out of shield volcanoes is thin, so it can travel for great distances down the shallow slopes of the volcano. Cinder cones are the simplest type of volcano. They occur when particles and blobs of lava are ejected from a volcanic vent. The lava is blown violently into the air, and the pieces rain down around the vent. Lava domes are created by small masses of lava which are too viscous (thick) to flow very far. Unlike shield volcanoes, with low-viscosity lava, the magma from volcanic domes just piles up over and around the vent. Caldera is the lava pit into which the active vent pours hot lava. Composite volcanoes or strato-volcanoes make up some of the world’s most memorable mountains: Mount Rainier, Mount Fuji, and Mount Cotopaxi, for example. These volcanoes have a conduit system inside them that channels magma from deep within the Earth to the surface. 3. The groundwater stored in the rock is released onto the surface at points where the water table reaches the surface. In this context, what do you mean by a ‘Vauclusian Spring’? (a) In areas of tilted strata, where permeable and impermeable rocks alternate, water emerges at the base of the permeable layers. (b) In Karst regions, water flows through passages in the rock by solution re-emerging when limestone gives place to some impermeable rock. (c) When a dyke or sill of impermeable rocks is intruded through permeable rocks. (d) Water emerging at the foot of the scarp in chalk escarpments. Answer: (b) Explanation: There are several types of springs: In areas of tilted strata, where permeable and impermeable rocks alternate; water emerges at the base of the permeable layers. In well jointed rocks, water comes through the joints. In limestone or Chalk escarpments, water issues at the foot of the scarp as Scrap-foot spring. The correct option is (b). In Karst regions, river often disappears underground. Such river water flows through passages in the rock by solution re-emerging when limestone gives place to some impermeable rock. They are called as Vauclusian Springs or Resurgence.
4. Which of the following create favourable conditions for the formation of ‘Deltas’? (1) Sea adjoining the delta should be shallow. (2) The coast should be favourable to tides. (3) Strong currents running at right angles to the river mouths Select the correct answer using the code given below: (a) 1 only (b) 1 and 3 only (c) 2 and 3 only (d) 1, 2 and 3
Answer: (a) Explanation: A river delta is a landform that forms from deposition of sediment carried by a river as the flow leaves its mouth and enters slower-moving or stagnant water. Statement 1 and 2 are correct. The necessary conditions for delta formation are: • Sea adjoining the delta should be shallow. • The coast should be sheltered and preferably tide-less. • No strong currents running at right angles to the river mouths. Hence, statement 3 is incorrect. 5. There are two places A and B. A is located on 50°E longitude while B is located on 10°W longitude. If winds blow with equal speed at these two places then (a) relatively more Coriolis force will be experienced by wind at place A (b) relatively more Coriolis force will be experienced by wind at place B (c) wind at both places A and B will experience same Coriolis force (d) cannot be determined Answer: (d) Explanation: Coriolis force is an apparent force caused by the earth’s rotation. The Coriolis force is responsible for deflecting winds towards the right in the northern hemisphere and towards the left in the southern hemisphere. This is also known as ‘Ferrel’s Law’. The Coriolis force is absent at the equator but increases progressively towards the poles. The magnitude of Coriolis force depends on the speed of wind and latitude (and not longitude) where the wind blows. The information about latitude is not given in the question text. Hence, it cannot be determined that wind at which place will experience more Coriolis force.