The process that continually adds new crust is

The correct answer is D. Where air pressure is low the air rises, cools as it goes up and the moisture in it condenses, so low pressure brings cloudy skies and wet weather, while in a high pressure area the air sinks and warms, clouds do not form and the sky stays clear and sunny. Air pressure is the weight of the column of air on a unit area, measured in millibars with a barometer and drawn on maps as isobars. Pressure falls as height increases, and it also falls when the air is heated, because warm air expands and becomes lighter. A is wrong because wind always blows from a high pressure area to a low pressure area. B is wrong because heated air rises instead of sinking, which creates low pressure and not high. C is wrong because cold air is heavy and sinks, so cold regions carry high pressure. Exam tip: heat and rising air mean low pressure and rain, cold and sinking air mean high pressure and clear skies.

The correct answer is B, L waves. Earthquake waves fall into body waves, which travel through the interior of the Earth, and surface waves, which move along the surface, and the surface waves are called L waves, or long waves. They are produced where the body waves meet the surface, they travel slowest and so reach a seismograph last, yet they are the most destructive, because near the ground they shake buildings sideways and up and down. The body waves are the P and S waves. P waves are the fastest, arrive first, are longitudinal and pass through solids, liquids and gases, while S waves are transverse and cannot pass through a liquid, which is how the liquid outer core was detected. A is wrong because P waves are primary body waves. C is wrong because S waves are secondary body waves. D is wrong because there is no class of earthquake waves called M waves. Exam tip: the order of arrival is P first, S next and L last, and L does the most damage.

The correct answer is A, four. The Bureau of Indian Standards code IS 1893 divides the country into four seismic zones, numbered II, III, IV and V, where Zone V carries the highest risk and Zone II the least. Zone V covers the Kashmir valley, the western and central Himalayas, the whole north east, the Rann of Kutch and the Andaman and Nicobar Islands. Zone IV takes in the rest of the Himalayan belt, Delhi, parts of Bihar and north Bengal, Zone III the Indo-Gangetic plain and much of the peninsular coast, and Zone II the stabler interior of the peninsula. An older map had five zones, and Zone I was merged into Zone II in the revision of 2002. B is wrong because two zones would be far too coarse for a country of this spread. C is wrong because no sixth zone is marked on the map. D is wrong because the five zone map was dropped when Zone I went. Exam tip: the zones run from II to V, and V is the most dangerous.

The correct answer is C, Panthalassa. In the continental drift theory that Alfred Wegener put forward in 1912, the single land mass was Pangaea and the single mega ocean around it was Panthalassa, a Greek name meaning all sea. Wegener held that Pangaea began to break up about 200 million years ago, first into Laurasia in the north and Gondwanaland in the south, with the Tethys Sea between them, and the pieces then drifted to their present places. He offered the jigsaw fit of the Atlantic coasts and matching rocks and fossils as proof, but the forces he named, the pole fleeing force and the tidal force, were too weak to convince geologists, and plate tectonics later replaced the theory. A is wrong because Pigmalion is not a geological name at all. B is wrong because Panama is an isthmus, and a country, joining North and South America. D is wrong because Pangaea was the land mass, not the ocean. Exam tip: fix the pair - Pangaea the super continent, Panthalassa the super ocean.

The correct answer is C, 15 degrees. The Earth turns through 360 degrees in 24 hours, so it covers 15 degrees of longitude in one hour, and each standard time zone is drawn one hour, that is 15 degrees, wide. One degree of longitude takes four minutes, the figure used to work out local time from the Greenwich meridian. India keeps a single clock, Indian Standard Time, based on the 82 degrees 30 minutes east longitude that passes near Mirzapur in Uttar Pradesh, which puts IST five and a half hours ahead of Greenwich time. Large countries such as Russia and the United States run several time zones. A is wrong because 24 is the number of zones, not the degrees in each. B is wrong because a belt of 20 degrees would give 18 zones, not 24. D is wrong because a belt of 10 degrees would give 36 zones. Exam tip: remember the pair - 15 degrees to an hour, one degree to four minutes.