Fossils

What do fossils tell us?

Fossils give clues about organisms that lived long ago. They help to show that evolution has occurred. They provide evidence about Earth. They help scientists understand what past environments were like.

Why are fossils not found in metamorphic rock?

the conditions (high temp, high pressure), usually destroy or deform fossils

How old are coal deposits?

30 million years

How tall would a 60 meter tree be after it is compressed during the formation of coal deposits?

60 centimeters

What type of creature was discovered in 2006?

a massive carnivorous sea creature that lived some 150 million years ago

Sediment

an animal is buried by sediment, such as volcanic ash or silt, shortly after it dies. Its bones are protected from rotting by the layer of sediment

What is a trace fossil?

an animal makes a footprint in sand or mud, and the footprint is eventually buried in layers of sediment, and the sediment becomes solid rock

What is tar (preserved remain)?

an organism is preserved by being trapped in a tar pit and dying, and the tar soaks into its bones and stops the bones from decaying

What is amber (preserved remain)?

an organism is preserved by being trapped in a tree's sticky resin and dies, more resin covers it, sealing the insect inside, and hardens it

What is ice (preserved remain)?

an organism is preserved by dying in a very cold region and the body is preserved by freezing

Describe three factors that encourage the formation of fossil formation

animals or plants dying in places low in oxygen, lower humidity levels, and slow decomposition

What temperature allows the enzymes in microbes to work most efficiently?

approximately 40 degrees celsius (104 degrees fahrenheit)

How does a cast form?

as the result of a mold. Water with dissolved minerals and sediment fills the mold's empty spaces. Minerals and sediment that are left in the mold make a cast. It is the opposite of its mold

What do all living things contain?

carbon

What tools do scientists use to gather information to provide us with clues to the appearance and extinction of prehistoric plants or animals?

chisels, hammers, maps, and relative or radiometric dating techniques

What is water full of?

dissolved minerals

Erosion

erosion from rain, rivers, and wind wears away the remaining rock layers. Eventually, erosion or people digging for fossils will expose the preserved remains

What are coal deposits?

fossilized remnants of entire forests

What do paleontologists use to study Earth's past?

fossils found in rocks

What types of tissue decompost last?

hard tissue like bones, shells, stems, or seeds

How does humidity effect microbes?

higher humidity levels speed up decomposition

How can an organism become part of a sedimentary layer?

it is covered by sediment before it fully decomposes

Where can you find areas that are low in oxygen and therefore inhibit decomposition?

lake bottoms, tree resins, and tar pits

Layers

more sediment layers accumulate above the animal's remains and minerals such as silics slowly replace the calcium phosphate in the bones

Movement

movement of tectonic plates or giant rock slabs that make up Earth's surface, lifts up the sediments and pushes the fossil closer to the surface

What type of highly accurate dating method has been used to determine the age of fossils?

radiometric dating

What type of rock contains the majority of fossils?

sedimentary rocks

Does rapid decomposition or slow decomposition result in increasing the likelihood of an organism fossilizing before it is totally decomposed?

slow decomposition

What types of tissue decompose first?

soft tissue like leaves, skin, muscles, and organs

What do trace fossils show?

the activities of organisms

What does the water seep through?

the layers of sediment to reach the dead organism. When the water evaporates, only the hardened minerals are left behind

Fossil

the preserved remains of a once-living organism

What are most fossils formed from?

the remains of animal's shell or bones or plant's woody stem and seeds

Why are fossils rarely formed in igneous rocks?

there is very little chance that an organism's remains will be preserved

Petrified

turning into stone

How do carbon films form?

when an organism dies and is buried in sediment, the materials that make up the organism break down. Eventually, only carbon remains, the thin layer of carbon left behind can show an organism's delicate parts

How does a mold form?

when hard parts of an organism are buried in sediment such as sand, silt, or clay. The hard parts completely dissolve over time, leaving behind a hollow area with the organism's shape.

How does decomposition occur?

when microscopic organisms break down plant and animal remains

When do petrified fossils form?

when minerals replace all or part of an organism