Continental Clues
This supercontinent existed about 280–245 million years ago and shows how continents once fit together like puzzle pieces.
Pangaea
The ocean discovery that revealed a continuous underwater mountain chain running through ocean basins (name).
Mid-ocean ridge (example: Mid-Atlantic Ridge).
Most tectonic plates move at this rate of speed
A few centimeters per year (cm/year).
Early evidence for plate tectonics included matching fossils and matching this other category across continents (two-word phrase)
Landforms (matching landforms and rock types).
Name two types of matching features found on different continents that supported the idea continents were once joined (one is a type of preserved organism, the other is a rock feature).
Fossils and matching landforms/rocks (or mountain ranges).
Where (what feature) does new oceanic crust form when magma rises and cools at a mid-ocean ridge?
Rift valley (or the mid-ocean ridge crest where new crust forms).
Name the three basic types of relative plate motion that occur at plate boundaries.
Move toward (convergent), move apart (divergent), slide past horizontally (transform).
This technology now directly measures plate speeds and directions and provides modern evidence for plate motion (three-letter acronym).
GPS
When geologists find the same-aged rocks and mountain chain shapes on separated continents, this is evidence that these continents once were
Joined or once connected.
What kind of deep ocean feature forms where a dense oceanic plate sinks beneath another plate?
Deep-ocean trench (formed at convergent/subduction boundaries).
Which type of plate boundary (moving toward, apart, or sliding past) produces deep-ocean trenches and volcanic mountain chains near the trench?
Plates moving toward each other (convergent boundaries with subduction).
Explain briefly how the pattern of ocean-floor rock ages (younger near ridges, older near trenches) supports the theory of plate tectonics.
Younger rock near mid-ocean ridges and older rock near trenches indicates continuous creation of new crust at ridges and movement away from ridges toward trenches (sea-floor spreading).
Explain briefly why continental shelves and their connecting ridges help scientists reconstruct past positions of continents.
Continental shelves and their ridges align when continents are pieced together; their matching shapes and ridge connections show past adjacency.
Explain how sea-floor spreading moves older rock away from the ridge and creates patterns of ocean-floor age.
New rock forms at ridges and pushes older rock away, producing symmetric age patterns: youngest at ridge, older farther away; magnetic striping and ages mirror each side.
Describe how gravity and the elevated, warmer rock at mid-ocean ridges help drive plate motion.
Ridge push: elevated warm rock at ridges sits higher and its weight pushes plates away; slab pull: sinking plate edge pulls the rest of the plate into the mantle. Both plus convection currents drive motion.
Describe how subduction recycles oceanic crust back into Earth's interior and how this process links to volcanic mountain formation.
Subduction: cool dense oceanic lithosphere sinks into mantle, melts, and generates magma; magma rises to form volcanic arcs parallel to trenches and causes earthquakes.
Describe what you would expect to happen to landforms and processes when two continental plates move toward each other. Give one specific example of a landform that forms this way and the process that creates it.
Expect mountain building (continental collision produces tall folded mountain ranges) and earthquakes. Example: Himalaya formed by collision of India and Eurasia; process = crustal shortening and uplift from plate convergence.
Sea-floor spreading begins with stretching and a long narrow valley. Name that valley and describe two processes that happen there
Rift valley; earthquakes and volcanic eruptions / lava cooling to form new oceanic crust.
Using plate motion concepts, predict what will happen to the shapes, sizes, and relative positions of South America, Africa, and the Atlantic Ocean if current plate motions continue.
South America and Africa: Atlantic Ocean will widen as plates at the mid-Atlantic ridge push them apart; evidence: presence of Mid-Atlantic Ridge (sea-floor spreading), GPS measurements showing plate motion away from ridge, and symmetric age patterns of ocean floor.
List and describe the three forms of evidence for plate tectonic theory?
Fossil Evidence, GPS, Mountain Range Similarity evidence, Sea Floor Spreading with alternating magnetic polarity, Continental Drift Theory