Plate Techtonics
What is the type of plate boundary where two plates move away from each other and new crust forms?
What is a Divergent Boundary
On a map of ocean-floor ages, where is the youngest crust found: near mid-ocean ridges or near continental shelves? Why?
Near mid-ocean ridges — new crust forms there at divergent boundaries.
What landform is formed when two continental plates push together?
Folded mountain ranges (e.g., Himalayas).
What happens to the water table if groundwater discharge equals recharge? (Choose: rises, falls, or stays the same.)
The water table stays the same.
What is a "dead zone" in the ocean?
A low-oxygen area where most marine life cannot survive because decomposition of excess organic matter uses up dissolved oxygen.
Name the process where molten rock rises at mid-ocean ridges and creates new oceanic crust.
Sea-floor spreading (or volcanic upwelling at a divergent boundary).
If rock layers in a cliff are numbered top = 1 to bottom = 4, which layer contains the oldest fossils? Explain using the Law of Superposition.
Layer 4 (bottom) is oldest because in undisturbed sedimentary layers, older layers are below younger layers.
Match these features to boundary types: Mid-Atlantic Ridge; San Andreas Fault; Pacific Ring of Fire. (Give the boundary type for each.)
Mid-Atlantic Ridge — divergent boundary; San Andreas Fault — transform boundary; Pacific Ring of Fire — convergent boundaries (subduction zones) and associated volcanic arcs.
Give one human activity from the list that most directly increases nutrient runoff into rivers and oceans and explain how that leads to dead zones.
Using fertilizers on farms increases nutrient runoff; excess nutrients (nitrogen, phosphorus) cause algal blooms, whose decomposition uses up dissolved oxygen and creates dead zones where fish cannot survive.
Which human activity from the choices most directly harms commercial fishing by causing dead zones? Explain briefly.
Excess fertilizer runoff from agriculture — it fuels algal blooms that decompose and deplete oxygen, killing fish and harming fisheries.
Which of these is strong evidence that continents were once joined: matching fossils across oceans, modern mountain heights, or tides? Briefly explain.
Matching fossils across oceans — identical fossils found on different continents indicate those landmasses were once connected.
Two sectors on opposite sides of a mid-ocean ridge show the most recently formed rock. Which sectors (closest or farthest from the ridge) are newest and why?
Sectors closest to the ridge are newest because magma rises and forms new crust at the ridge; older crust moves outward.
How do hotspots (like Hawaii) form island chains? Include why the islands get older along the chain.
A stationary hotspot in the mantle produces magma that forms a volcano as the plate moves over it. As the plate keeps moving, the original volcano moves away from the hotspot and becomes extinct while a new volcano forms over the hotspot — so islands farther from the hotspot are older.
Identify two actions from the list that improve water quality and explain why each helps.
Disposing of wastes properly — prevents contaminants from entering water. Testing underground fuel tanks for leaks — detects and prevents fuel contamination of groundwater.
After fertilizer runoff increases algae growth, explain two ways the stability of the shoreline ecosystem is reduced.
(1) Reduced oxygen (hypoxia) causes loss of species diversity and fish kills, disrupting food webs. (2) Excess algae blocks sunlight, harming aquatic plants and primary producers, which weakens energy flow and resilience.
Describe how the discovery of identical rock types and fossils in West Texas and eastern Antarctica supports plate tectonics. Then name the boundary type most likely responsible for mountain building in those areas.
Identical fossils and rock chemistry suggest the areas were once adjacent before plates separated—supporting continental drift. The mountains likely formed at convergent (continental-continental) boundaries (collision).
The ocean crust ages outward from ridges up to about 280 million years. Explain how this pattern supports sea-floor spreading and plate tectonics.
The symmetric age pattern (young at ridges, older farther away) indicates new crust is continually formed at ridges while older crust moves away, matching predictions of sea-floor spreading and plate movement.
Which boundary type is most likely to produce volcanic arcs and deep ocean trenches? Give an example region.
Convergent (oceanic-continental or oceanic-oceanic subduction) boundaries produce volcanic arcs and deep trenches. Example: The Andes (oceanic-continental) and the Mariana Trench/Mariana Islands (oceanic-oceanic).
A region's population grows and water demand increases. Explain one likely negative effect on water resources and one practical solution.
Negative effect: Aquifers may be over-pumped and depleted, lowering the water table and reducing supply for ecosystems and wells. Solution: Implement water conservation measures (water-saving appliances, irrigation efficiency) and recharge protection (limit impermeable surfaces, protect recharge zones).
Read this scenario and choose the BEST explanation: A shoreline community has fewer fish and less species diversity after fertilizer runoff. Which statement best explains the change in ecosystem stability?
With less oxygen and light and fewer different types of living things, the ecosystem becomes less stable because it has reduced biodiversity and weakened food-web connections, so it is less able to recover from disturbances.
Explain why transform boundaries (like the San Andreas Fault) cause earthquakes but do not usually create tall mountain ranges. Include a short diagram description (words only) of how the plates move.
Transform boundaries slide past each other horizontally, causing shear stress and earthquakes; because plates move side-by-side rather than colliding or pulling apart, vertical crustal uplift is limited, so tall mountain ranges rarely form. Diagram (words): Two blocks side-by-side with arrows pointing opposite directions along the fault line showing lateral motion.
A cross-section shows magma rising at a mid-ocean ridge and pushing plates apart. Describe how seafloor spreading can lead to the formation of a new ocean basin over millions of years.
As divergence continues, new ocean crust is added and the distance between continental margins grows; continued spreading can widen a rift into a narrow sea and eventually a full ocean basin as oceanic crust replaces former continental crust between the continents.
Describe how mountains can form from the collision of plates. Include a brief explanation of how similar fossils on separated continents provide evidence for past plate positions.
When continental plates collide, crust is compressed, folded, and thickened, pushing rock upward to form mountains. Finding the same fossils and rock types on now-separated continents indicates those landmasses were once joined and later separated by plate motion, consistent with mountain-building during collisions.
Which management action from the list would best reduce nitrate contamination from agriculture and why?
Encouraging legislation that supports water quality control (combined with farmers using best practices like buffer strips, reduced fertilizer application timing) — laws can require and fund nutrient management, reducing runoff and nitrate leaching into water.
A forest ecosystem experiences a drought lasting several months. During this time, water becomes a limiting factor. Which of the following best explains how this disturbance would most likely affect the ecosystem's stability?
A. Plant populations would decrease due to lack of water, which would cause herbivore populations to decrease because there is less food available.
B. The ecosystem would remain stable because organisms are adapted to survive in their environment no matter what happens.
C. Herbivore populations would increase because there would be less competition for the remaining plants.
D. Only the plant populations would be affected because plants need water to survive, but animals would remain unaffected.
Plant populations would decrease due to lack of water, which would cause herbivore populations to decrease because there is less food available.