Across
- 4. Steep hill that is flat on the top
- 5. Permanently frozen ground
- 8. Rainfall in reservoirs under the ground
- 9. Bright pink burnt clay above a coal bed
- 10. Between the mountains
- 12. Beginning of a river
- 13. Deep holes dug out by the wind
- 14. Level areas between mountains that have few trees
- 16. Basin formed by a collapsed volcano
- 17. Wearing away of rock and soil by wind and water
- 18. Low water reservoir that turns to a salty mud flat or a dry lake as water evaporates in summer
Down
- 1. Cold, treeless plains
- 2. Rock formed by hot melted material that has cooled and hardened
- 3. Holes in a lava-bed from which hot gas steams up
- 6. Rock formed by deposits laid down by water
- 7. Rock that has been changed by heat and pressure
- 9. Patches of hard lava rock on the land surface
- 11. Canyons with steep walls
- 15. Steep-sided inlets