Q1.
Physical map of Australia. Based on the colours you see, what conclusions can you draw about the landforms?
Answer
Using the colour key from page 2, Fig. 1.34 tells a clear story about the continent.
- A vast dry interior. Almost the whole middle of the continent is red, orange and pale tan — the colours of desert and bare, arid ground, and it is labelled the GREAT AUSTRALIAN DESERT. Since this covers most of the map’s land area, a large part of Australia must be desert or arid.
- A thin green rim. Green appears only as a narrow strip along the east coast, and in smaller patches in the south-west and south-east corners. So the well-watered plains, forests and farmland — and therefore most of the people — are squeezed against the coasts.
- Higher land near the east coast. Along the eastern edge the green darkens into a brown, ridged strip running north to south, which marks land standing higher than the plains around it.
- No white anywhere. There is no ice or permanent snow on the map, so Australia has no mountains high enough or latitudes cold enough to hold them — it is the flattest and lowest of the inhabited continents.
- Shallow warm water in the north-east. Off the north-eastern coast the blue is paler, and the Great Barrier Reef is labelled along it — shallow, warm, sunlit water is exactly where corals can build.
Why it happens: the two patterns — dry middle, green rim — have the same cause. The higher land along the east coast stands in the way of the moist winds blowing in from the sea. The air is forced to rise, cools and drops its rain on the seaward side, which is why that strip is green; by the time the air crosses the ridge it has little moisture left, so the interior lies in a rain shadow. On top of that, Australia straddles the Tropic of Capricorn, one of the two belts where dry air sinks and clouds rarely form. A continent that is both tropic-straddling and cut off from the sea winds can hardly be anything but desert in the middle.
Did you know? The chapter’s DON’T MISS OUT on page 30 warns against assuming ‘desert’ means hot. The largest desert on Earth is Antarctica — over 14 million square kilometres, more than four times the area of India — and it is the coldest desert of all. What defines a desert is how little precipitation it gets, not how warm it is.