fossil – n. part of an animal or plant from the past that has been preserved in rock

geologic – adj. the study of rocks and the physical processes of the earth

lava – n. hot melted rock that comes out of a volcano

extinction – n. a situation in which a type of animal no longer exists

species – n. a group of animals or plants that are similar and can produce young animals or plants

stream – n. a small river

mammal – n. a kind of animal that feeds milk to its young and that usually has hair or fur covering most of its skin

graze – v. to eat

stressful – adj. something making a person stressed

hostile – adj. unpleasant and not suitable for living or growing