Across
1
Largest river in South America
5
Imaginary line around the middle of Earth
6
Low-lying land surrounded by higher ground
7
Where river meets the sea
9
Flat grassland in tropical regions
10
Distance east or west of prime meridian
Down
2
Line dividing two countries
3
Land surrounded by water on three sides
4
Low area between mountains
8
Region surrounding the North Pole
11
Large area covered with trees
12
Narrow sea inlet between cliffs