what are the four eras, from the past to the present
- precambrian
- paleozoic
- mesozoic
- cenozoic
when was the canadian shield formed?
the precambrian era
when were the appalachian mountains formed?
the paleozoic era
when were the rocky and innuitian mountains formed?
the mesozoic era
when were the rocky mountains completely formed?
the cenozoic era
how long ago was the precambrian era?
4600-570 million years ago
how long ago was the paleozoic era?
570-245 million years ago
how long ago was the mesozoic era?
245-66 million years ago
how long ago was the cenozoic era?
66 million years ago-present
when were the first single organisms evolved?
the precambrian era
when were the first multi-celled organisms evolved?
the precambrian era
when were the first plants and animals evolved?
the paleozoic era
when were the first fish, insects and amphibians evolved?
the paleozoic era
when did the first mammals and birds evolve?
the mesozoic era
when did the first flowering plants evolve?
the mesozoic era
when did modern mammals take over the earth?
the cenozoic era
when did the human age begin?
the cenozoic era
when did cratons (large land masses) form due to volcanic activity?
the precambrian era
when was most of north america covered in warm, shallow seas?
the paleozoic era
when were shallow seas inside north america?
the mesozoic era
when did earth first have a stabilized atmosphere?
the mesozoic era
when did large reptiles dominate the earth until a major extinction event?
the mesozoic era
when did pangaea break up?
the cenozoic era
when do ice ages occur, currently?
about every 100 000 years
