Rock Cycle
This rock type forms when magma or lava cools and solidifies.
What is Igneous Rock?
This is the theory that explains the movement of Earth's lithospheric plates.
What is the theory of plate tectonics?
In undisturbed sedimentary layers, are the oldest rocks generally at the top or bottom?
What is the bottom?
What is a half-life?
Time required for half of the radioactive parent atoms in a sample to decay.
What is a fossil?
Preserved remains, impressions, or traces of past life.
These two processes turn loose sediments into sedimentary rock.
What are compaction and cementation?
This is the type of plate boundary that forms when two plates move apart.
What is a divergent plate boundary?
Name the principle used to order undisturbed sedimentary layers from oldest to youngest.
What is the Law of superposition?
After one half-life, what percentage of the original parent isotope remains?
50%
Why are fossils most commonly found in sedimentary rocks?
Sediments can bury and preserve remains; heat and melting associated with other rock formation often destroy remains.
A sedimentary rock is buried and subjected to heat and pressure without melting. This is the type of rock that forms.
What is a metamorphic rock?
Matching fossil species are found on continents separated by an ocean. How does this support plate tectonics?
The continents were once connected or closer together and later moved apart.
Layers A, B, and C were deposited bottom to top. An intrusion cuts A and B but not C. Is the intrusion older or younger than B? Explain.
Younger than B; cross-cutting relationships.
A mineral contains 25% of its original parent isotope. How many half-lives have passed?
2 half-lives
Name TWO characteristics that make a fossil useful as an index fossil.
Widespread geographically and lived for a relatively short geologic interval (also distinctive/easily identified).
Describe the 5 processes that can change an igneous rock into a sedimentary rock.
What are weathering, erosion, deposition, compaction, and cementation?
At a convergent boundary between two continental plates, what major landform commonly develops, and why?
Mountain ranges; collision compresses and uplifts crust.
A fault cuts layers A through D but does not cut overlying layer E. When did faulting occur relative to D and E?
After D formed and before E was deposited.
A parent isotope has a half-life of 8 million years. A mineral contains 12.5% of its original parent isotope. Estimate its age.
24 million years
The same index fossil appears in rock layers at two distant sites. What can geologists infer about those layers?
They formed during approximately the same time interval.
A metamorphic rock melts, cools, weathers, and its sediments are cemented. Identify the rock type after cooling and the final rock type.
What is an igneous rock after cooling and a sedimentary rock as the final?
A coastline contains folded marine sedimentary rocks high above sea level. Use TWO pieces of evidence to explain how the area changed.
Marine fossils/rocks indicate former underwater deposition; folding and uplift indicate tectonic compression and elevation change.
Sequence these events oldest to youngest: deposition of layer X; deposition of layer Y above X; intrusion cutting both; erosion surface truncating intrusion; deposition of layer Z above erosion surface.
X, Y, intrusion, erosion, Z.
A rock sample has 6.25% of its original parent isotope remaining. If its half-life is 2.5 million years, estimate its age.
10 million years old.
Marine fossils occur in rock now found on a mountain. Explain what this reveals about past environments and how the land changed.
The rock was deposited in a marine environment and later uplifted, commonly through tectonic processes.