Geologic Time Scale
Fossil Formation
Index Fossils
Dinosaur Speed Challenge
Using fossils to DATE
100
What is the geologic time scale and why is it important?
The geologic time scale is a timeline that organizes Earth's history into eons, eras, periods, and epochs. It measures major events like mass extinctions, evolution, and geological changes.
100
In which fossilization method leaves organics behind in a thin, black film?
Carbonization.
100
What is an index fossil?
A fossil used to define and identify geologic periods; must be widespread, short-lived, and easily recognizable.
100
What formula do we use to estimate the speed of a dinosaur from its footprints?
Alexander's Formula.
100
What is the difference between relative dating and absolute dating?
Relative dating compares rock layers to determine which is older, while absolute dating gives an actual age in years using radiometric techniques.
200
List the four eons of Earth's history in order from oldest to youngest.
Hadean, Archean, Proterozoic, Phanerozoic.
200
What is the difference between a mold and a cast fossil?
A mold is an impression left in rock, while a cast is when that impression is later filled with minerals creating a replica.
200
Name two examples of index fossils we found on our hike in the Kaibab Limestone.
Rugosa corals, Brachiopods, crinoids, gastropods
200
If a dinosaur's stride length is 2.8 meters and its hip height is 1.2 meters, estimate if it was walking or running.
LS/HH = 2.333 = RUNNING!!
200
Imagine you discover a new fossilized creature unlike anything seen before. What steps would you take to determine its age and significance? (Give 2 steps.)
1) Use index fossils and stratigraphy to estimate its relative age.
2) Use radiometric dating technology to get an absolute age.
300
Why are fossils from the Precambrian time so rare? Name at least two reasons.
1) Most early life was soft-bodied and did not fossilize well.
2) Rocks from that time were heavily altered by heat and pressure.
3) Erosion has destroyed many older rocks.
300
Describe how a trace fossil forms and what it can show about an organism.
A trace fossil forms from evidence of an organism's activity, like footprints, burrows, or feces, that are preserved in sediment.
300
Why are index fossils more useful than regular fossils for dating rocks?
Because they only existed during a short, specific time period and can date rocks precisely.
300
You find a t-rex dinosaur trackway with footprints 1.5 meters apart. The footprint length is 0.6 meters. Estimate the hip height.
hip height = 4×footprint length = 2.4 m
300
Why is the fossil record considered incomplete? Give two reasons.
Many organisms did not fossilize because conditions weren't right (soft-bodied organisms especially).
Erosion, metamorphism, and other natural processes have destroyed many fossils.
400
Name a major event that marks the end of the Mesozoic Era.
A mass extinction event likely caused by an asteroid impact, which led to the extinction of the dinosaurs.
400
What conditions would best preserve a full animal (like a mammoth)?
Rapid burial in sediment and freezing, tar pits, or amber to prevent decay.
400
Which Southern Utah index fossil looks like a symmetrical clam? Which are asymmetrical?
Brachiopods, Bivalves
400
Why would using dinosaur stride length alone without hip height give an inaccurate speed estimate?
Because stride length depends on body size — larger animals naturally have longer strides even if moving slowly.
400
A fossil is found between two volcanic ash layers dated at 150 million years and 140 million years. How old is the fossil likely to be?
Between 140 and 150 million years old (likely around 145 million years if centered).
500
Fill in the missing period: Cambrian, Ordovician, __________, Devonian, ____________, Permian.
Silurian, Carboniferous
500
Name all 6 types of fossilization along with a description of what they are.
Permineralization, mold, cast, carbonization, trace fossils, preserved remains
500
Ammonites belong to which group of animals? What did they evolve into?
Mollusks — specifically cephalopods (squids, octopi)
500
Little Foot from the Land Before Time has a stride length of 0.5 meters and foot size of 15 cm. Using the formula, what is Little Foot's average speed? (Earth's g = 9.8 m/s^2)
0.44 m/s
500
How can scientists use fossils to learn about ancient environments? Give two examples.
Certain fossils (like coral reefs) indicate warm, shallow seas.
Leaf shape and size in fossilized plants can show what ancient climates (like tropical vs. dry) were like.