Extremely difficult earths history Crossword

This printable crossword puzzle on the topic of Rocks & Minerals has 13 clues. Answers range from 4 to 13 letters long. This crossword is also available to download as a Microsoft Word document or a PDF.

high carboniferous
The great dying, _______extinction
Armored invertebrate
Era of Dinosaurs
first period of Mesozoic
This time periods remnants provide man with coal and fossil fuels
epoch of the ice age
Time of stegosaurus
time of the first amphibians
Planet with which Earth collided with to form the moon
Supercontinent of the Precambrian and Cambrian
Gondwana's later counterpart
mammal-like__________