430 likes | 657 Views
Geologic Time. What is Geologic Time?. A relative scale which divides geologic time into units. Relative time is compared to something. Units are from largest to smallest Eon Era Period Epoch Age. Basis for subdivision. Law of superposition
E N D
What is Geologic Time? A relative scale which divides geologic time into units. Relative time is compared to something. Units are from largest to smallest Eon Era Period Epoch Age
Basis for subdivision Law of superposition Age of Earth 4.6 billion yrs Age of oldest rock 4 billion yrs Extinctions
Precambrian Era Vast time in earth history before the deposition of Cambrian Fossil bearing rocks. Fossils are rare because animals were soft bodied. Example: Jellyfish, paramecium, and trail marks from animals.
Paleozoic Era Life increased in complexity The continents collided to form Pangea Also has “Age of fishes” in it Divided into 6- 7 periods
Cambrian Period- 600 mya 1st common and widespread fossils example: Algae, sponges, worms, mollusks All lived in the Sea Trilobites- large but few bivalves- clams sea cucumbers
Ordovician Period 500-425 mya Rise of new animals groups of importance. Oldest vertebrates- fragments of bone example: bryozoans, brachiopods, echnoids Sea covered land uplift and mountain building
Silurian Period 425-405 mya New families rather than new groups of animals Most important plants (fossil of oldest plant) Trilobites, crinoids, etc. from ancient reefs near Chicago types of fish starting
trilobites Live fossil
crinoids live fossil
Devonian Period 405-345 mya Expansion of fish and land plants 1st land animals (primitive amphibians) First developed fish Jawless fish plate-skinned fish sharks 1st boney fish From lobed-fin fish -amphibians
Devonian continued Oldest spiders, millipedes and insects Fresh water clams Great forests starting Coral reefs
Carboniferous 345-280mya Mississippian period 345-310 mya Shallow warm seas Sea animals and plants flourish Amphibians and land plants spread Coal swamp forests (most US under water) Pennsylvanian Period 310-280 mya Scale trees, seed ferns develop Giant dragonflies (30 inch wing span) Reptiles from amphibians
Permian Period 280-230 mya Primitive conifers New insects (beetles, and true dragonflies) Active reptiles different from skull and vertebrae fossil eggs example: sail-back lizard (sail as temperature control) Theriodonts – carnivore ( mammals are descendents) A lot become extinct (trilobites, corals, blastoids)
Mesozoic Era Known as middle Life Also has the “Age of the Reptiles” in it. New pattern of lands and seas, formed mountains ranges
Triassic Period 230-180 mya A lot of volcanic activity Reptiles dominate advanced body structure shell-protected eggs both land and water reptiles 1st appeared lobster like creature Conifer forest- Petrified forest
Jurassic Period 180-145 mya Flying reptiles and herbivores in water Oldest mammals-fragments of rat sized jaws and teeth. Oldest known bird Over thousand species of insects
Dinosaurs 3 main groups 1. Sauropods: long-necked, long-tailed, four-legged (largest land animal 87 ft long) 2. Stegosaurs: armored reptiles, weighed up to 10 tons 3. Carnivorous Theropods: walk on hind legs
Dinosaurs hips Dinosaurs are also classified by the two types of hips. Saurischian- lizard hipped ornithischian- bird hipped
Cretaceous Period 135-63 mya Major advanced of sea New arrivals- flowering plants, trees-magnolia, oaks, maple, etc. New sources of food provided for mammals, birds, reptiles, and insects Dinosaurs roamed over all continents Small mammals, marsupials At the end of period extinction of dinosaurs.
Cenozoic Era 63-1 mya ( last 70 my) Two Periods and seven epochs Includes the age of the Mammals Includes the age of Man Birds are numerous Boney fish dominate Our era of today
Tertiary Period Has five epochs. A lot of changes taking place examples: -Small mammals to large mammals -Tropical plants to grasses -Single animals to herds -Alps, Himalayas, Rockies, Andes and Glacier formation
Paleocene epoch Mammals are small Tropical plants
Eocene Epoch Mammals becoming larger Ancestors of modern whale and horse
Oligocene Epoch Tropical plants replaced by grasses and pines Apes, elephants, cats and dogs families
Miocene Epoch Herds of grass eating animals Land bridge between Siberia and Alaska- Mastodans cross.
Pliocene Epoch Glaciers began to form Sea level fell Animals crossed land bridges and new land formed Animals hunting herds (Near End of Epoch) Ice age begins Grand canyon was carved out of rising rock layers
Quarternary Period Includes two Epochs Climate much colder Includes the Ice Age Includes the age of man Our period of today
Pleistocene Epoch 2.5 mya Ice Age Glaciers advanced at least four different times Animals either developed protective covering or moved south example: mastodons, saber-tooth tigers, mammoths (At end of the epoch) 10,000 yrs ago Ice sheets melting Large mammals became extinct
Holocene Epoch Earth’s climate became warmer Human civilization arose (Age of man) The epoch of today