UPSC STATIC QUIZ – Geography : 29 February 2024

Solution: c)

Sinkholes are depressions formed in the ground when layers of the Earth’s surface start collapsing into caverns. They can occur suddenly and without warning, because the land under the surface of the Earth can stay intact for a period of time until the spaces get too big.

Sinkholes can be formed due to natural processes or human activity. Typically, sinkholes form in areas of “karst” terrains, where the rock below the surface of the Earth can be easily dissolved by groundwater.

Essentially, this means that when rainwater seeps into the ground, the rock below the surface of the Earth starts dissolving, leading to the creation of spaces. This process is a slow and gradual one and can sometimes take hundreds or thousands of years.

Solution: b)

Statement 3 is incorrect.

For those on Earth, Venus is the second-brightest object in the sky after the moon. It appears bright because of its thick cloud cover that reflects and scatters light. But while Venus, which is the second closest planet to the Sun, is called the Earth’s twin because of their similar sizes, the two planets have significant differences between them.

For one, the planet’s thick atmosphere traps heat and is the reason that it is the hottest planet in the solar system, despite coming after Mercury, the closest planet to the Sun. Surface temperatures on Venus can go up to 471 degrees Celsius, which is hot enough to melt lead, NASA notes.

Further, Venus moves forward on its orbit around the Sun but spins backwards around its axis slowly. This means on Venus the Sun rises in the west and sets in the East. One day on Venus is equivalent to 243 Earth days because of its backward spinning, opposite to that of the Earth’s and most other planets. Venus does not have a moon and no rings.

Solution: b)

Statement 3 is incorrect.

Asteroids are rocky objects that orbit the Sun, much smaller than planets. They are also called minor planets.

Asteroids are divided into three classes.

• First are those found in the main asteroid belt between Mars and Jupiter, which is estimated to contain somewhere between 1.1-1.9 million asteroids.
• The second group is that of trojans, which are asteroids that share an orbit with a larger planet. NASA reports the presence of Jupiter, Neptune and Mars trojans. In 2011, they reported an Earth trojan as well.
• The third classification is Near-Earth Asteroids (NEA), which have orbits that pass close to the Earth. Those that cross the Earth’s orbit are called Earth-crossers. More than 10,000 such asteroids are known, out of which over 1,400 are classified as potentially hazardous asteroids (PHAs).

Solution: b)

Statement 3 is incorrect.

Along much of the Ring of Fire, tectonic plates move towards each other creating subduction zones. One plate gets pushed down or is subducted by the other plate. This is a very slow process – a movement of just one or two inches per year. As this subduction happens, rocks melt, become magma and move to Earth’s surface and cause volcanic activity.

Subduction zones are also where most of the violent earthquakes on the planet occur. The December 26, 2004 earthquake occurred along the subduction zone where the Indian Plate was subducted beneath the Burma plate.

Solution: c)

Quasars are very luminous objects in faraway galaxies that emit jets at radio frequencies. They are found in galaxies that have supermassive blackholes which power these bright discs. However, 90 per cent of them do not emit strong radio waves, making this newly-discovered one special.

Most active galaxies have a supermassive black hole at the centre which sucks in surrounding objects. Quasars are formed by the energy emitted by materials spiralling around a blackhole right before being sucked into it.