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grade 7 ch 4

a trip through geologic time

sedimentary rock type of rock made of hardened sediment
how do fossils form when living things die and are buried by sediments
fossils preserved remains or traces of living things
where are fossils found? in rock
list types of fossils molds, casts, petrified fossils, carbon films, trace fossils
what is a mold a HOLLOW AREA of sediment in the shape of an organism or part of an organism, such as a shell, is buried in sediment
what is a cast a SOLID COPY OF THE SHAPE of an organism. it's the opposite of it's mold.
petrified fossils fossils in which minerals REPLACE all or part of an organism
carbon film an extremely THIN COATING of carbon on rock.
trace fossils provide evidence of the ACTIVITIES of ancient organisms.
What are 3 ways in which the remains of an organism can be preserved with little change amber (~sap), freezing, tar
what do fossil records tell us they provide EVIDENCE about the history of LIFE and PAST ENVIRONMENTS on earth. they also shows that the different groups of organisms have changed over time.
geological time scale record of the life forms and geologic events in Earth's history.
how was geological time scale developed? scientists studied rock layers and index fossils worlds wide, the placed the rock's in order by relative age. Later, radioactive dating helped determine the absolute ages of the divisions in the geologic time scale.
eras units of time.
what is the order of the eras, Cenozoic era, Paleozoic era, and Precambrian, Mesozoic era PPMC P.P.M. See
out of the eras, PMC, which era was the longest, shortest? C (Cenozoic) shortest P (Paleozoic) longest
periods eras subdivided into units of geologic time.
name the periods with the Cenozoic Era QT (quaternary (4), Tertiary (3rd)) ceno=recent mammals
name the periods within the Mesozoic Era CJT (Cretaceous, Jurassic, Triassic) (messo=middle) age of the reptiles
what does Paleo mean ancient or early
what are the different units of the geologic time scale eras, periods
when did the earth form? roughly 4.6 billion years ago, about the same time as the other planets and the sun.
How did the sceintists determine the age of the Earth? radioactive dating
how did the earth form? First it was dust, rock & ice, that gravity pulled together. As it grew larger, it's gravity increased pulling in more dust, rock & ice. the energy from the collisions turned from kinetic to thermal energy, causing the earth's temperature to rise.
what force caused the material that formed Earth to come together? gravity
what physical features formed during Earth's first several hundred million years? atmosphere, oceans and continents (AOC)during the Prcambrian time.
Comet a ball of dust and ice that orbil the sun, has carbon dioxide.
oceans absorbed most of what element from the comets carbon dioxide
continental drift process of continents moving very slowly over the earth's surface because of forces inside Earth. a few centimeters per year!
When or where did life on Earth begin? noone knows, but single cell organisms (like bacteria) were found in rocks formed 3.5 billion years ago!
why did oxygen increase on Earth the organisms began to make their own food from photosynthesis.
what does ozone block out UltraViolet rays (UV)
what do scientists think were the first organisms to evolve on earth? bacteria
collisions of dust, rock and ice caused heat, the planet became very _____? hot
what happened to the hot materials? they are heavy, so they sank to the center of the earth
the heat on the outside of the earth cooled from losing the heat to space, what is the less dense, molten material called that hardened on the earth's outer layer solid crust and mantle
volcanic eruptions release what? carbon dioxide, water vapor and other gases
what do comet collisions cause? other gases added to atmosphere
Created by: ellenhester