Natural Hazards

Contour trenching involves digging pits or trenches along the contour lines of a slope. These trenches accumulate runoff water, allowing it to infiltrate the soil rather than flowing down the slope and causing erosion. Bench terracing creates level platforms, contour terracing follows contours, and leveling creates flat surfaces - but specifically digging pits on slopes for runoff accumulation is contour trenching.

Soil erosion in India is caused by multiple human activities and natural factors. Deforestation (2) removes vegetation that holds soil, while overgrazing (4) destroys protective grass cover and compacts soil. Excessive rainfall (1) can accelerate erosion, and excessive cultivation (3) depletes soil structure. The combination of factors 2 and 4 represents major anthropogenic causes.

Tornadoes have the highest wind velocities among all atmospheric disturbances, often exceeding 300 km/h. Typhoons, hurricanes, and cyclones are all tropical cyclones with similar wind speeds, but tornadoes can have significantly higher wind velocities in their most intense forms.

 Bunds, dams and drains are constructed to prevent gully erosion.

Cyclones affect the eastern coast, particularly Jharkhand and Northern Orissa (3). Droughts are common in the Mid-eastern India region (1). Earthquakes frequently occur in the Himalayan foothill zone (4), which is tectonically active. Floods are common in the plains of Uttar Pradesh and Bihar (2) due to their river systems.

Statement 1 is incorrect because shocks originate at the hypocenter (focus), not the epicenter. The epicenter is the point on the surface directly above the hypocenter. Statement 2 is correct - earthquake foci can be in the crust or upper mantle. Statement 3 is correct - plate margins are indeed more earthquake-prone.

Stone dams are specifically constructed to control the formation and expansion of gullies and ravines. They help reduce erosion velocity, allowing water to slow down and soil to settle. While they indirectly affect sheet erosion, their primary purpose is gully and ravine control in degraded lands.

Hurricanes are the specific name for cyclonic storms that occur in the North Atlantic Ocean, particularly in the West Indies and Gulf of Mexico region. The same storm is called a typhoon in the western Pacific and simply a cyclone in the Indian Ocean.

The cultivation is done on the steep slopes so that the water should not remain stagnant and no soil erosion would be there.

Volcanoes release various materials during eruptions, including molten lava, gases, steam, dust, and rock fragments. Different eruptions may produce different combinations of these materials, so 'all of the above' is the most comprehensive answer.

Statement 1 is correct - moderate earthquakes do occur along constructive plate boundaries. Statement 3 is correct - disastrous earthquakes are typically caused along destructive (convergent) plate boundaries. Statements 2 and 4 are incorrect as they don't accurately describe the relationship between plate boundary types and earthquake severity.

Magma is called lava when it reaches the Earth's surface (crust). Magma is the molten rock beneath the surface, while lava is the same material once it erupts and flows on the surface. The core and inner portion are too deep, and mantle is where magma originates.

S waves (shear waves) can only travel through solid materials and are absorbed by liquids. The statement 'S waves propagate through liquids' is therefore false. P waves (primary waves) can travel through both solids and liquids, moving material parallel to their direction. L waves (surface waves) travel along Earth's surface.

Volcanic eruptions produce materials in all three states of matter: solid (pyroclastics like ash and rocks), liquid (lava/molten rock), and gas (water vapor, CO2, sulfur dioxide). This makes option C the correct answer.