1. List (and provide a brief description of the general topography in) each of the physiographic regions of Arkansas. See Arkansas Geologyppt
  2. Ozarks Plateau(Boston Mountain Plateau, Springfield Plateau, and Salem Plateau)
  3. Arkansas River Valley
  4. Ouachita Mountains
  5. Gulf Coastal Plain
  6. Mississippi River Alluvial Plain
  7. List the rock types and explain how they are formed. Name one rock example in each type.
  8. Igneous – from magma
  9. extrusive (ex. Pumice) cools quickly above ground, small to no crystals
  10. intrusive (ex. Granite) cools slowly underground, large crystals
  11. Sedimentary – from sediment deposited in water
  12. compaction (ex. Shale),
  13. cementation (ex. Sandstone and Limestone)
  14. crystallization (ex. Gypsum),
  15. Metamorphic – from heat and pressure
  16. regional metamorphism from pressure(Shale (Sed) → Slate (Meta) →Phyllite - Schist (Meta) → Gneiss (Meta) → magma
  17. contact metamorphism from heat (ex. Quartz (Sed) → Quartize (Meta)
  18. Define
  19. Relative Dating: Determining the age of materials by putting them in a sequence in order of which event took place form most recent to oldest (comparative not exact) Relative dating observes the placement of fossils and rock in layers known as strata.
  20. Absolute Dating: Radiometric dating, or numeric dating, determines an actual or approximate age of an object by studying the rate of decay of radioactive isotopes, such as uranium, potassium, rubidium and carbon-14 within that object. Radioactive isotopes decay at a fixed rate. This rate provides scientists with an accurate measurement system to determine age. For example, carbon dating is used to determine the age of organic materials. Once something dies, it ceases taking in new carbon-14, and the existing carbon-14 within the organism decays into nitrogen at a fixed rate. Scientists measure the proportion of carbon-14 left in the organism to determine its age.
  21. Law of Superposition: The lower layers in any particular cross section of rock are older than the upper layers in that cross section.
  22. Law ofOriginal Horizontality:Sedimentary layers are horizontal, or nearly so, when originally deposited. Cross sections that are not horizontal have been deformed by movements of the Earth’s crust (fold, faults, erosion)
  23. Law of Uniformitarianism: the present is the key to the past.
  24. Law of Cross Cutting Relationships:geologic features, such as faults and igneous intrusions are younger than the rocks they cut.
  25. Law of Included Fragments (inclusions): A rock layer with pieces of another rock layer inside it is younger than the pieces. Pieces of a rock layer inside another rock layer are older than the rock layer they are inside.
  26. Principle of faunal succession: groups of fossil plants and animals occur in the geologic record in a definite and determinable order. If there are fossils embedded in the rock, these fossils (inclusions) are younger than the rock they are embedded in but are older than the rock above them. If a fault, fold or erosion occurs, fossils may be used to help “match” up rock layers.
  1. Put in order from oldest to youngest. Include any erosion, faulting, tilting or folding.

D – oldest – at the bottom – Law of Superposition
A – next to bottom – Law of Superposition
B – (just above A) Law of Horizontality
Tilt – plate tectonics
E – intrusion – Law of Cross Cutting Relationships
Erosion – not horizontal/straight line – Law of Horizontality
B –Law of Horizontality
Erosion – not horizontal/straight line – Law of Horizontality
C – intrusion – Law of Cross Cutting Relationships
Erosion - Law of Horizontality

DABEC (old to young)
E and C are igneous intrusives (magma rising)
A (sandstone), B (limestone) and D (shale) are sedimentary (layers)

  1. Which rock layers are the same ages? How do you know?

1 and 8, 2 and 9, 3 and 10

  1. Put in order from oldest to youngest. Remember to include any erosion, faulting, tilting or folding!

FEDCBA

Igneous – D

Sedimentary – ABCEF
Top: Erosion

What Happened Here?

A is younger than C (Superposition)
C is younger than I (Inclusions)
I is younger than D, E and B (Cross – Cutting)
D is younger than E and B(Cross – Cutting)
H, F, K and J have been tilted or folded (Original Horizontality)
G is younger than B, H, F, K and J (Baked Contacts)
Sequence from youngest to oldest: A, C, I, D, E, G, B, tilting, H, F, K, J