Maps and place knowledge

347213

提示Each extra digit splits the square into tenths, so 700 m along the bottom becomes a 7.

为什么The first three figures give the easting: square 34, then seven tenths across, so 347. The last three give the northing: square 21, then three tenths up, so 213. Along the corridor before up the stairs, and never mix the two halves.

Six

提示Add one more digit to each half of a four-figure reference.

为什么A four-figure reference names a whole 1 km square. Adding an extra digit to each half splits that square into tenths, so the reference locates you to within 100 m.

45 minutes

提示One centimetre on this sheet stands for 250 m on the ground - find the real distance first.

为什么A scale of 1:25 000 makes 1 cm worth 25 000 cm, which is 250 m, so 12 cm is 3000 m - three kilometres. Three kilometres at 4 km/h takes three quarters of an hour. Serious walkers then add roughly a minute for every 10 m of climbing.

steep

提示The lines are squeezed because you gain a lot of height over very little ground.

为什么Each contour joins points of equal height, so lines close together mean a big height change across a short distance. Widely spaced contours mean gentle, easy walking.

The Arctic Ocean

提示Frozen over for much of the year, it sits at the top of the globe around the North Pole.

为什么It is ringed by Russia, Canada, Greenland and Alaska, and much of its surface is sea ice. In size order the five oceans run Pacific, Atlantic, Indian, Southern and Arctic - the Pacific alone covers about a third of the planet.

23.5 degrees north

提示Roughly a quarter of the way from the Equator to the top of the globe, where the midsummer sun sits straight overhead.

为什么The Tropics of Cancer and Capricorn, at 23.5° north and south, mark the furthest points where the sun can ever be directly overhead; the poles sit at 90°. Longitude is measured the same way from the Prime Meridian at Greenwich.

Glasgow

提示Not the capital - the industrial city on the River Clyde in the west.

为什么Edinburgh is Scotland's capital, but Glasgow on the Clyde holds more people. The four UK capitals are London for England, Edinburgh for Scotland, Cardiff for Wales and Belfast for Northern Ireland.

The mantle

提示The thick, slowly creeping layer that carries the plates on its back.

为什么It is by far the thickest layer, made of hot rock that flows a few centimetres a year. Convection currents within it are what drag the plates about.

A constructive boundary

提示New rock rises to fill the gap, so land is being made rather than destroyed.

为什么At a constructive (divergent) boundary such as the Mid-Atlantic Ridge, magma rises into the gap and cools into fresh crust. Iceland is being widened by one right now.

The Sahara

提示Its name is simply the Arabic word for desert.

为什么It is the largest hot desert on Earth, roughly the size of the United States. South of it lies the dry grassland of the Sahel, and further south again the Congo rainforest.

The Himalayas

提示It holds Everest and separates the subcontinent from Tibet.

为什么The range was thrown up where the Indian plate crashed into Asia, and it is still rising. It blocks cold northern air and shapes the monsoon that waters India.

Russia

提示It spans eleven time zones, from the Baltic to the Pacific.

为什么It covers about an eighth of the world's land, though much of that is Siberian forest and tundra. Most of its people live in the European west, near Moscow and St Petersburg.