Continental Drift
Who first proposed the idea that continents once formed a single landmass and later drifted apart?
Alfred Wegener.
List the three main layers of Earth's interior from outermost to innermost.
Crust, mantle, core.
What instrument records seismic waves?
Seismograph (or seismometer).
What is the process by which new oceanic crust forms at mid-ocean ridges called?
Sea-floor spreading (formation of new crust at mid-ocean ridges).
What is a tectonic plate?
A plate is a rigid piece of Earth's lithosphere that moves over the asthenosphere.
Name one type of evidence Wegener used to support continental drift (give one clear example)
Examples: matching fossils (e.g., Mesosaurus), similar rock types/mountains, matching glacial deposits, fit of coastlines
Which layer is liquid and generates Earth's magnetic field through its motion?
Outer core (liquid iron and nickel).
Name the two main types of body waves produced by earthquakes.
P-waves (primary, compressional) and S-waves (secondary, shear).
Describe what magnetic striping on the sea floor shows about sea-floor spreading.
Symmetrical stripes of normal and reversed magnetic polarity on either side of ridges record reversals and show crust is created and pushed outward.
Name the three types of plate boundaries and give one geological feature associated with each.
Divergent — mid-ocean ridge; Convergent — deep ocean trench or mountain range; Transform — fault (e.g., San Andreas).
Explain how the fit of continental coastlines supports the idea of past connection.
Coastlines such as South America and Africa appear to fit together like puzzle pieces, suggesting they were connected
Explain how temperature and pressure change with depth inside Earth.
Temperature increases and pressure increases with depth; deeper layers are hotter and under greater pressure.
Which seismic wave type cannot travel through liquids, and what does that reveal about Earth's interior?
S-waves cannot travel through liquids; shows outer core is liquid.
Explain how age of oceanic crust changes with distance from a mid-ocean ridge.
Oceanic crust is youngest at the ridge and gets progressively older away from the ridge.
Explain how plate tectonics provides a unifying explanation for continental drift, earthquakes, and mountain building.
Plate tectonics explains continental movement (plates carry continents), earthquakes (motion along plate boundaries), and mountain building (plate collisions uplift crust).
Describe how the distribution of similar fossils across different continents supports continental drift
Identical or very similar fossil species are found on now-separated continents, implying those landmasses were once joined.
Describe the difference between the lithosphere and the asthenosphere and why that difference matters for plate motion
Lithosphere = rigid outer shell (crust + uppermost mantle); asthenosphere = ductile, partially molten layer beneath that allows lithospheric plates to move.
How can scientists use the arrival times of P-waves and S-waves at different stations to locate an earthquake epicenter? (Brief outline)
Measure arrival times of P and S waves at three or more stations; differences give distance to epicenter; triangulate intersection of circles to find location.
What role do mid-ocean ridges and subduction zones play together in the cycling of oceanic crust?
Mid-ocean ridges produce new crust; subduction zones recycle old oceanic crust back into the mantle, maintaining a balance.
Describe how a convergent boundary between two continental plates forms mountain ranges, using an example.
When two continental plates converge, crust crumples and thickens, forming large mountain ranges (example: Himalayas from India colliding with Eurasia).
Why did many geologists originally reject Wegener’s idea?
Lacked a convincing mechanism for how continents moved
Using evidence from seismic wave behavior, explain how scientists infer the presence of Earth's solid inner core.
P- and S-wave travel patterns: S-waves do not pass through outer core (liquid); P-wave speed changes and refraction indicate a dense inner core; timing and shadow zones allow inference of a solid inner core.
Explain how seismic wave shadow zones provide evidence for a liquid outer core, including which waves and shadow patterns are involved.
: S-wave shadow zone (about 104°–140° from epicenter) and P-wave refraction create zones with no arrivals or delayed arrivals, indicating a liquid outer core and a solid inner core from differential behavior.
Describe one method scientists use to determine the age of sea-floor rocks and how that method supports spreading.
Methods: radiometric dating (e.g., K-Ar), magnetic reversal stratigraphy correlated with geomagnetic polarity timescale; both show age patterns increasing away from ridges.
Discuss how plate motions can lead to volcanic activity at both subduction zones and mid-ocean ridges, noting differences in magma composition and eruption style.
Subduction zones: oceanic plate melts, producing more silica-rich magma and explosive volcanism (volcanic arcs). Mid-ocean ridges: decompression melting of mantle produces basaltic magma and less explosive eruptions.