Daily Quiz #25 UPSC Prelims Marathon – November 29, 2019

Explanation: Coral reefs are built by and made up of thousands of tiny animals—coral “polyps”—that are related to anemones and jellyfish. Polyps are shallow water organisms which have a soft body covered by a calcareous skeleton. The polyps extract calcium salts from sea water to form these hard skeletons. The polyps live in colonies fastened to the rocky sea floor. The tubular skeletons grow upwards and outwards as a cemented calcareous rocky mass, collectively called corals. When the coral polyps die, they shed their skeleton [coral] on which new polyps grow. The cycle is repeated for over millions of years leading to accumulation of layers of corals.

Fringing reefs grow near the coastline around islands and continents. They are separated from the shore by narrow, shallow lagoons. Fringing reefs are the most common type of reef that we see. It is a coralline platform lying close to the shore extending outwards from the mainland. It is sometimes separated from the shore by a shallow lagoon. It is widest when fringing a protruding headland but completely absent when facing the mouth of a stream. The outer edge grows rapidly because of the splashing waves that continuously renew the supply of fresh food.

Explanation: Zeugen are tabular masses which have a layer of soft rocks lying beneath a surface layer of more resistant rocks. Difference in erosional effect of the wind on soft & resistant rock surfaces, carve them into weird looking ridge & furrow landscape. Mechanical weathering initiates their formation by opening up joints of the surface rocks. Wind abrasion further eats into underlying softer layer so that deep furrows are developed. The hard rocks then stand above the the furrows as ridges or Zeugen. Zeugen may stand 10 to 100 feet above the sunken furrows. Continuous abrasion by winds gradually lowers the Zeugen & widens the furrow.

Explanation: The Bab el-Mandeb Strait is a sea route chokepoint between the Horn of Africa and the Middle East, connecting the Red Sea to the Gulf of Aden and Arabian Sea.

Explanation: The driest place on Earth is in Antarctica in an area called the Dry Valleys, which have seen no rain for nearly 2 million years. There is absolutely no precipitation in this region and it makes up a 4800 square kilometer region of almost no water, ice or snow. While some areas of the Atacama along the coast have succulent plants like cacti, the more arid parts of the desert have no vegetation. These parched regions do not even have cyanobacteria – green photosynthetic microorganisms that live in rocks or under stones in most other deserts.