Week-1 Assignment-1_Solution.pdf

Assignment – 1_Solution (Earth Sciences for Civil Engineering (Hindi)) 1. _________ and _________ epochs belongs to the Quaternary period. (a) Holocene and Pleistocene (b) Pliocene and Miocene (c) Holocene and Miocene (d) Pliocene and Pleistocene Answer: (a) Holocene and Pleistocene. Exp...

Assignment – 1_Solution (Earth Sciences for Civil Engineering (Hindi)) 1. _________ and _________ epochs belongs to the Quaternary period. (a) Holocene and Pleistocene (b) Pliocene and Miocene (c) Holocene and Miocene (d) Pliocene and Pleistocene Answer: (a) Holocene and Pleistocene. Explanation: The Quaternary period is divided into two epochs, from youngest to oldest i.e., the Holocene and Pleistocene. 2. The “Supernova” explosion took place at around _________ years ago. (a) 7 billion (b) 7 million (c) 12 billion (d) 12 million Answer: (a) 7 billion. Explanation: At around 7 billion years ago an explosion occurred which was called as “Supernova”. 3. When magma rises from deep in the mantle, it fprms new oceanic crust at _________ (a) Collision zone (b) Subduction zone (c) Transform plate boundary (d) Mid-oceanic ridges Answer: (d) Mid-oceanic ridges. Explanation: The production of new seafloor and oceanic lithosphere results from mantle upwelling in response to plate separation. The melt rises as magma at the linear weakness between the separating plates, and emerges as lava, creating new oceanic crust and lithosphere upon cooling also called Mid-oceanic ridges. 4. Ocean ridge system is a continuous belt of _________ km and it is a prominent feature in ocean (a) 6500 km (b) 65 km (c) 65,000 km (d) 650 km Answer: (c) 65,000 km. Explanation: The first discovered mid-ocean ridge was the Mid-Atlantic Ridge, which is a spreading center that bisects the North and South Atlantic basins; hence the origin of the name 'mid-ocean ridge'. The mid-ocean ridge system thus is the longest mountain range on Earth, reaching about 65,000 km (40,000 mi). 5. Seismic waves characterize the internal structure of the earth and nature of its layers, which suggest that the outer core and the inner core are ______________respectively. (a) liquid and solid (b) solid and liquid (c) plastic and liquid (d) liquid and plastic Answer: (a) liquid and solid. Explanation: Inner core is the centre and the hottest layer of the Earth. The inner core is solid and made up of iron and nickel with temperatures up to 5,500oC. The outer core of the Earth is similar to a very hot ball of metals, whose temperature is around 4000oF to 9000oF. The outer core is so hot that the metals inside are all liquid. 6. Low-density rocks float _________ and have _________ roots, whereas high-density rocks float _________ and have _________ roots. (a) high, deep, low, shallow (b) low, deep, high, shallow (c) high, shallow, low, deep (d) low, shallow, high, deep Answer: (a) high, deep, low, shallow. Explanation: Because of isostasy, all parts of the lithosphere are in a floating equilibrium. Low-density wood blocks float high and have deep roots, whereas high-density blocks float low and have shallow roots. 7. The principle of isostasy governs the rise or subsidence of the _________ until the mass is buoyantly balanced. (a) Outer Core (b) Lower Mantle (c) Mantle (d) Crust Answer: (d) Crust. Explanation: The principle of isostasy governs the rise or subsidence of the crust until the mass is buoyantly balanced. Because of isostasy, all parts of the lithosphere are in a floating equilibrium. 8. The Geodynamo system involves interactions between the _________ and _________. (a) Crust and Mantle (b) Upper Mantle and Lower Mantle (c) Inner and outer core (d) Continental and oceanic crust Answer: (c) Inner and outer core. Explanation: The dynamo mechanism that generates the Earth's magnetic field: Convection currents of fluid metal in the Earth's outer core, driven by heat flow from the inner core, organized into rolls by the Coriolis force, generate circulating electric currents, which supports the magnetic field. 9. The heat flowing out of the Earth’s _________ causes convection that generates and maintains the magnetic field. (a) Inner Core (b) Upper Mantle (c) Lowe Mantle (d) Outer Core Answer: (d) Outer core. Explanation: The dynamo mechanism that generates the Earth's magnetic field: Convection currents of fluid metal in the Earth's outer core, organized into rolls by the Coriolis force, generate circulating electric currents, which supports the magnetic field. 10. The _________ discontinuity marks the boundary between Outer and Inner core. (a) Mohorovicic (b) Repetti (c) Lehmann (d) Gutenberg Answer: (c) Lehmann. Explanation: It is the transition zone between outer and inner core. The Lehmann discontinuity is an abrupt increase of P-wave and S-wave velocities at the depth of 220 km.