science exam review
Terms
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- topsoil
- cumbly, dark brown soil that is a mixture of humus, clay, and other minerals
- ice wedging
- when wedges of ice widen or deepen in cracks
- loess
- fine, wind-deposited sediment
- Half-life
- The time it takes for half of the radioactive atoms to decay.
- Invertebrate
- Animals without backbones
- Quaternaty Period
- A period from 1.8 million years ago to the present. The glaciers advance and retreat over much of North America and Europe, parts of South America and Asia, and all of Antarctica. Mammals, flowering plants and insects dominate land. Modern humans evolved in Africa about 100,000 years ago. Giant mammals of North America and Eurasia become extinct when the ice age ends about 10,000 years ago.
- Jurassic Period
- Period covers 208 million through 144 million years ago. Pangaea breaks apart as North America separates from Africa and South America. Largest dinosaurs thrived, including Stegosaurus, Diplodocus, and Apatosaurus. First birds appear. First flying reptiles, pterosaurs, appear.
- chemical weathering
- the process that breaks down rock through chemical changes
- fault
- a break in the earth's crust
- weathering
- the process that breaks down rock and other substancees at earth's surface
- Cretaceous Period
- Period from 144 million to 66 million years ago. Continents move toward their present-day positions as South America splits from Africa. Widespread volcanic activity occurs. First flowering plants appear. Dinosaurs, including Tyrannosaurus rex, dominate. First snakes appear. Mass extinction at the end of the period causes disappearance of many land and marine life forms, including dinosaurs.
- paleontologist
- scientists that study fossils
- Index fossil
- A fossil that is widely distributed and represents a type of organism that existed only briefly
- abrasion
- the grinding away of rock by rock particles carried by water, ice, wind, or gravity
- mold
- a hollow area in sediment in the shape of an organism or part of and organism
- absolute age
- the exact age of a rock
- unconformity
- the surface where new rock layers meet a much older rock surface beneath them
- cast
- a solid copy of the shape of an organism
- humus
- a dark-colored substance that forms as plant and animal decay
- decomposers
- the organisms that break down the remains of dead organisms
- soil conservation
- the managment of soil to prevent it's destruction
- deflation
- the process by which wind removes surface material
- Mesozoic era
- An era that covered the time from 245 million to 66 million years ago. This era included the Triassic, Jurassic, and Cretaceous periods.
- intrusion
- A mass of igneious rock that is formed when magma pushes into body of rock and cools and hardens there. An intrusion is always younger than the rock layers around and beneath it.
- loam
- soil that is made up of about equal parts of clay, sand, and silt
- law of superposition
- scientists use this to determine the relative age of sedimentary rock layers
- extinct
- when a species no longer exsits
- contour plowing
- when farmers plow their fields along curves of a hill
- petrified fossil
- fossils in which minerals replace all or part of an organism
- dust bowl
- a serious drought in the 1930's in the great plains and all of the soil was blown away
- erosion
- the removal of rock particles by wind, water, ice, or gravity
- litter
- the layer of plant decay on the surface
- Tertiary Period
- The period from 66 million to 1.8 million years ago. The Rocky Mountains and Himalayas form. Continents continue to move into present-day positions. Continental glaciers cover Antarctica. Flowering plants thrive. First grasses appear. Age of mammals begins. Modern groups such as horses, elephants, bears, rodents and primates appear. Ancestors of humans evolve.
- relative age
- the age of a rock compared to other rocks
- Era
- The basic units of geologic time scale after pre-Cambrian time.
- sedimentary rock
- the type of rock that is made from hardend sediment
- evolution
- the gradual change in living things over long periods of time
- Cambrian Period
- Life took a big leap forward at the beginning of the Paleozoic era, a great number of different kinds of organisms evolved
- Silurian Period
- Period from 438 million through 408 million years ago. Coral reefs develop. Early continents collide with what is now North America forming mountains. Fish with jaws develop. Land plants appear. Insects and spiders appear.
- sod
- a thick mass of roots at the surface of the soil
- trace fossil
- provide evidence of the activities of ancient organisms
- extrusion
- An extrusion is lava that hardens on the surface. An extrusion is always younger than the rocks below it.
- Period
- Eras are subdivided into units of geologic time call periods.
- Geologic time scale
- A record of the lifeforms and geologic events in Earth's history.
- Mass extinction
- At the end of the Paleozoic era when many kinds of organisms died out. This mass extinction affected both plants and animals on land and in the seas.
- subsoil
- consists of clay and other minerals
- Precambrian time
- Pre-Cambrian time covers from 4.6 billion to 544 million years ago. During this time life developed as bacteria and softbodied, multicelled organisms. First mass extinction probably occurred near the end of the Precambrian
- soil horizon
- a layer of soil that differs in color and texture from above and below it
- Ordovician Period
- Period from 505 million through 438 million years ago. Warm, shallow seas cover much of the earth. Ice cap covers what is now North Africa. In vertebrates dominate the oceans. Early vertebrates -- jawless fish -- become common.
- Carboniferous Period
- Period from 360 million through 286 million years ago. Appalachian Mountains began to form. North America and northern Europe ally and a warm tropical region. Great swamp forests of huge woody trees cover eastern North America and parts of Europe. First true reptiles appear. Winged insects appear.
- Devonian period
- Period from 408 million through 360 million years ago. Seas rise and fall over what is now North America. Age of fishes begans as sharks and fish with scales and bony skeletons become common. Trilobites and corals floors in the ocean. Lungfish develope. First amphibians reach land.
- Triassic Period
- Period from 245 million to 208 million years ago. Pangaea holds together for much of the Triassic. Hot, dry conditions dominate the center of Pangaea. Age of reptiles begins. First dinosaurs appear. First mammals, which evolved from warm-blooded reptiles, appear. First turtles and crocodiles appear. Conifers, palmlike trees, and ginkgo trees dominate forests.
- fossil
- preserved remains or traces of living things
- Radioactive decay
- A process where elements breakdown, or decay, over time by releasing particles and energy.
- bedrock
- the solid layer of rock beneath the soil
- Cenozoic era
- The era from 66 million years ago to present. This era covers the Tertiary and Quaternary periods.
- carbon film
- an extremely thin coating of carbon on rock
- Vertebrate
- An animal with the backbone.
- Permian Period
- Period from 286 million through 245 million years ago. Deserts become larger in tropical regions. The supercontinent Pangaea forms as all continents joined together. Reptiles become dominant on land. Warm-blooded reptiles appear. Mass extinction of many marine invertebrates, including trilobites.
- Paleozoic era
- A era of time from 544 million to 245 million years ago. This era included the Cambrian, Ordovician, Silurian, Devonian, Caroniferous and Permian periods.
- mechanical weathering
- the type of weathering which rock is physically broken into smaller pieces
- permeable
- material that is full of tiny, connected air spaces that allow water to seep through
- soil
- loose, weathered material on earth's surface in which plants can grow