Across
1
Imaginary line around the middle of Earth
3
Low-lying land surrounded by higher ground
6
Deep narrow valley with steep sides
8
Flat elevated area of land
9
Raised area of land, smaller than a mountain
10
Chain or group of islands
Down
2
Region between the two tropic lines
4
Largest ocean on Earth
5
Low area between mountains
7
Flat grassland in tropical regions
11
Region surrounding the North Pole