🌍 Layers of the Earth
This thin, outermost compositional layer accounts for only about 1% of Earth's total volume.
What is the Crust?
The German scientist who proposed the hypothesis of Continental Drift in 1912.
Who was Alfred Wegener?
New oceanic crust is continuously created along these underwater mountain ranges.
What are Mid-Ocean Ridges?
Tectonic plates slide horizontally past one another along this type of conservative boundary (||).
What is a Transform Boundary?
The primary driving force of plate motion caused by thermal energy rising and cooling in the mantle.
What are Mantle Convection Currents?
At $12,000^\circ\text{F}$, the Inner Core remains in this physical state due to crushing planetary pressure.
What is a solid?
The name of the ancient supercontinent that existed roughly 250 million years ago, meaning "All Earth."
What is Pangaea?
Compared to rocks near mid-ocean ridges, rocks found far away near ocean trenches are noticeably this in age.
What is older?
When an oceanic plate meets a continental plate, the oceanic plate dives underneath because of this physical property.
What is higher density?
This driving mechanism occurs when the cold, dense edge of a subducting plate sinks and drags the rest of the plate down behind it.
What is Slab Pull?
This mechanical layer of the upper mantle is soft, warm, and ductile—behaving like warm silly putty or asphalt under pressure.
What is the Asthenosphere?
Finding fossils of Glossopteris and Mesosaurus on widely separated continents supported this line of evidence.
What is Fossil Correlation?
This type of boundary where plates pull apart (<-- -->) is responsible for seafloor spreading.
What is a Divergent Boundary?
The process where a denser plate sinks beneath a lighter plate back into the mantle.
What is Subduction?
Ocean trenches (like the Mariana Trench) and volcanic island arcs form at this specific boundary type.
What is an Oceanic-Oceanic Convergent Boundary (or Subduction Zone)?
Swirling movements of liquid iron and nickel in this layer generate Earth's global magnetic field.
What is the Outer Core?
Glacial striations (ice scratches) found in modern tropical regions like Southern Africa prove those landmasses were once located near this region.
What is the South Pole?
Stripes of alternating magnetic polarity frozen into iron-rich basalt on the ocean floor provided proof of seafloor spreading, known by this term.
What is Magnetic Reversals (or Paleomagnetism)?
California's San Andreas Fault is a famous example of this boundary type.
What is a Transform Boundary?
This driving mechanism occurs when gravity pushes warm, elevated crust outward away from the ridge axis.
What is Ridge Push?
The Lithosphere is composed of these two combined compositional structures.
What are the Crust and the rigid uppermost Mantle?
The primary reason the scientific community rejected Wegener’s continental drift hypothesis during his lifetime.
What is he could not explain the driving mechanism (how or why solid continents moved)?
This famous North American/African rift zone is an example of a modern continental rift valley beginning to form a brand-new ocean basin.
What is the East African Rift Valley?
The collision of two low-density continental plates at a convergent boundary produces this type of landform, such as the Himalayas.
What are Folded Continental Mountains/Tall Mountain Ridges?
Explain why continental crust is never subducted and recycled into the mantle, even when colliding head-on with oceanic crust.
What is continental crust is too thick, granitic, and low-density (buoyant) to sink into the mantle?