Geological History

1. A solid copy of the shape of an organism.
2. This is used to find the ages of human artifacts or things that were once living.
4. Provide evidence of the activities of ancient organisms.
7. Estimate of when the first living organisms showed up on the planet.
8. Fossilized dino dung or waste.
9. Fossils in which minerals replace all or part of an organism.
10. Several species of lobe-finned fish that use a simple lung to survive periods when their watery habitat dries by burying themselves in moist mud and breathing air.
11. Dinosaur extinction.
12. Parasitic fish that have skeletons made of cartilage but lack a proper skull.
14. The top rock layer and its fossils is the youngest and the bottom is the oldest.
15. Used to date fossils up to 1.26 billion years old.
18. Fossils of widely distributed organisms that lived during only one short period.
20. Continents join to form Pangaea.
23. Lava that hardens on the Earth's surface.
24. The surface where new rock layers meet a much older rock surface beneath them.

1. An extremely thin coating of carbon on rock.
3. Pangaea started to break apart.
5. Stones that are in the digestive systems of dinosaurs and help digest food (like grit for birds).
6. A time scale established by geologists that reflects a consistent sequence of historical periods.
13. Chronological collection of life's remains in sedimentary rock layers.
16. Age of Fishes.
17. Hollow area in sediment in the shape of an organism or part of an organism.
19. A break in the earth's crust.
21. An igneous rock layer formed when magma hardens beneath Earth's surface.
22. Shelled cephalopod animals that were the dominant invertebrate predators for millions of years.