History Of Earth Crossword

Grouping rocks by ages
Remains of a prehistoric organism
Determining the relative age of a fossil
Name a fossil
using index fossils to determine the age of a rock
A fossil of a type of fish
Only eats meat
Explosive land form that erupts molten rock, gases, and ash
Prehistoric animal
To be gone forever
The actual age of a rock or fossil or how long an event occurred
A way of measuring a rock or fossils age by comparing the amount of radioactive from of an element in the rock or fossil with the amount of its decay product.
Describes the age of an object or event in comparison to another object or event.
How many years ago did humans evolve?
Pointed mountains
Earth's age
Subdivision of geological age
When a lot of living things go extinct
Age of a fossil
Plants that live in a tropical area
A form of sedimentary rock
Name a fossil
Fossils of echinoderms
Layers of rock
A solid organic substance