Study Guide - Geological Time KEY
Name _________________________ Core 1 2 3 _____/ 50 pts.
Part A Geological Time Vocabulary: Add the geological term to match the definitions.
1. geologic time
scale
2. Radiometric
testing
3. stratigraphy
4. era
5. period
6. epoch
7. trilobite
8.fossil
9. exoskeleton
10. endoskeleton
11. plate tectonics
12. cyanobacteria
13. amphibians
14. reptiles
15. extinction
16. Pangaea
17. gymnosperm
18. angiosperms
19. mammal
20. marsupial
system of chronological measurement that uses both stratigraphy and radiometric
dating to describe the timing and relationships between events that have occurred
throughout Earth’s history is called
a method of dating geological or archeological specimens by determining the relative
proportions of particular radioactive isotopes present in a sample.
The study of rock layers (strata), especially the distribution, deposition, and age of
sedimentary rocks.
a long and distinct period of history with a particular feature or characteristic; several
hundred million years
subdivision of an era
subdivision of a period
extinct marine arthropod that occurred abundantly during the Paleozoic era, with a
carapace over the forepart, and a segmented hind part divided longitudinally into three
lobes.
the remains or impression of a prehistoric organism preserved in petrified form or as a
mold or cast in rock.
external skeleton
internal skeleton
a theory explaining the structure of the earth's crust and many associated phenomena
resulting from lithospheric plates that move over the underlying mantle.
blue-green algae a group of photosynthetic bacteria which release oxygen into the
atmosphere
a cold-blooded vertebrate animal that has an aquatic gill-breathing larval stage
followed by a terrestrial lung-breathing adult stage. Egg layers in water.
a cold-blooded vertebrate of a class that includes snakes, lizards, crocodiles, turtles,
and tortoises. They are distinguished by having a dry scaly skin, and typically laying
soft-shelled eggs on land.
the state or process of a species becoming extinct, no longer existing on the Earth.
a continent which included all the landmass of the earth prior to the Triassic period
a plant, such as a pine tree, whose seeds are not enclosed within an ovary, fruit.
a plant having its seeds enclosed in an ovary; a flowering plant.
a warm-blooded vertebrate animal of a class that is distinguished by the possession of
hair or fur, the secretion of milk by females for the nourishment of the young, and the
birth of live young.
a mammal of an order whose members are born incompletely developed and are
typically carried and suckled in a pouch on the mother's belly.
21. Which type of skeleton do our classroom pets have? Include at least 2 in each category.
Endoskeleton
Exoskeleton
Both
g-piggies, Penny the Hedgehog,
Connie & Sumer
Miss Adele, the giant cockroaches
Cowboy the tortoise; Omni, CB, &
Snappy the turtles
22. What is the key difference between angiosperms and gymnosperms? Angiosperms have the
seeds encased in an ovary (the fruit part – yum) example is an apple; Gymnosperms’ seeds do are not
enclosed in an ovary example is a pine tree’s pinecones.
23. What is the key difference between amphibians, mammals and reptiles? Amphibians lay
their eggs in water, reptiles lay their eggs on land, mammals carry their fertilized eggs and
embryos internal in the female’s uterus and give birth to live young.
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Part B Using a Geological Timelscale Chart: Use Handout I (Your “fuzzy” time scale sheet that
you get to write all over the front and use during the test!) to complete questions 24 - 25.
24. Create a timeline showing the 4 major eras in chronological order including time spans.
Eras
Pre-cambrian
Time Span: 4600 -- 540
MYBP MYBP
Paleozoic
540 -- 290
MYBP MYBP
Mesozoic
Cenozoic
245 - 146
MYBP MYBP
66 MYBP -- PRESENT
25. Complete the following table:
Key Organisms
Homo sapiens sapiens
Time ERA
Cenozoic
Trilobites
Paleozoic
Dinosaurs
Mesozoic
Mammals are dominant life forms
Cenozoic
Fish were dominant life forms
Paleozoic
Invertebrates , marine plants
Paleozoic
Part C Characteristics of Key Geological Eras – Complete the following chart.
Geological Era
26. Precambrian
26. Paleozoic
27. Mesozoic
28. Cenozoic
Key Characteristics
Earliest of geological periods when the Earth was primarily covered with vast
seas.
Included bacteria-like organisms and Ediacaran organisms develop.
Since there were few organisms with hard body structures, there are few fossils
from this era
There were several episodes of mountain building
Organisms with endoskeletons and exoskeletons are plentiful such as
amphibians and the key index fossil organisms, trilobites,
Most organisms were marine life-forms with fish becoming the dominant life form.
First land plants form and first insects evolve.
Sometimes called the age of dinosaurs
Included reptiles, amphibians, insects and the first mammals appeared on
the land masses
Most land based life forms during this period disappeared during the K–T
Extinction.
Atlantic Ocean begins to form, and Pangea breaks up
Sometimes called the Age of Mammals and Homo sapiens evolves.
This is the shortest time period.
Current time period.
Period also includes vertebrates, invertebrates, amphibians, and reptiles.
The Alps and Himalayas begin to rise.
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29. Why are cyanobacteria important? These photosynthetic microorganism produced most of the 1st
oxygen for our atmosphere.
30. Why are trilobites such good index fossils? They were plentiful, have distinct characteristics,
and are found in most regions world-wide; therefore, when they are found in strata, geologist
can infer that the layer is dated to the Paleozoic Era.
31. Why is there such a scarcity of fossils from the Pre-cambrian? Most all of the organisms
were micro-organism or soft bodied invertebrates that make poor fossils.
Part D Relative Dating – Complete the following table to summarize the key relative dating
principles.
Principle
Description in Your Own Words
Diagram demonstrating the
principle.
32. In undisturbed layers of rock, the
Superposition
highest layers are the youngest and
the lowest layer is the oldest.
33.
Cross-cutting
34. Any geological event or
material that goes through a layer
(strata) is younger than the strata
it goes through.
35.
36. Inclusions existed and are older
Inclusions
than the material that forms around
them.
37.
38. Strata (Earth layers) lays down
Original Horizontality
horizontally due to gravity and will
stay horizontal until acted up by a
plate tectonic event like an
earthquake or volcano.
39.
39. Use relative dating principles to create a relative
timeline.
C, F, A, D, G, B, E
40. Which principles did you use in # 39?
Superposition, Inclusions, Crosscutting
41.
Use relative dating principles to create a
relative timeline. Q, O, N, M, L, P, H, I, J, K
42. Which principles did you use in #41?
Superposition and crosscutting
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Part D Absolute Dating: See Page 4 by itself on the site!
43. Can you use relative dating principles to determine actual dates? Yes ____ No _____
44. What technique do geologists use to determine absolute dates for fossils and strata?
r_____________________________ t________________________
45. How long does it take a 100.00g sample of Arsenic to decay to 50g? (The half-life or
Arsenic = 33 seconds)
46. How many half-lives does it take a 200 g sample of Arsenic to decay to 25 g? (The halflife or Arsenic = 33 seconds)
Use the following table of commonly used isotopes for problems # 47– 49.
Radioactive Parent
Stable Daughter
Product
Half Life Values
U-238
Pb-206
45 Billion Years
U-235
Pb-207
713 Million Years
K - 40
Ar-40
1.3 Billion Years
C -14
N-14
5730 Years
47. How long would it take for a 50 g sample of K-40 to decay to 50% K-40 and 50% Ar-40?
48. How many half lives does it take a 500 mg sample of U-238 to decay to 125 mg ?
49. How long would it take for 4 half lives to occur for the isotope U-235?
50. How old do geologists estimate the Earth to be? ________________________________ What evidence
do they use to support this date? _________________________________________________________________________
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