Across
- 8. number of species in an area
- 9. forces that change the surface of the earth from within; i.e. divergent, convergent, and transform boundaries
Down
- 1. forces that change the surface of the earth from outside; i.e. humans, erosion, and weathering
- 2. species that are not native to a specific location and have a tendency to spread to a degree believed to cause damage
- 3. the variety of life in the world or in a particular habitat or ecosystem.
- 4. determining the age of rocks based on the decay of the elements
- 5. the process of new crust forming at a ridge and pushing older crust out
- 6. the length of time it takes for one-half of a radioactive element to change into another element
- 7. when all the species have died out