Lesson 4 of 6 · Plate tectonics & the rock cycle
A landscape with more than one history
8 minute lesson · 3 checks along the way
Your goal for this lessonConnect plate motion and surface processes with several possible rock transformations, without treating the rock cycle as a compulsory sequence.
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A moving surface on a solid planet
Earth’s tectonic plates are pieces of : crust plus rigid uppermost mantle. They move relative to one another, carrying ocean floors and continents. At divergent boundaries plates separate; at convergent boundaries they approach; at transform boundaries they slide past. Convergence can involve a plate sinking beneath another or continents colliding and thickening the crust. A boundary label describes relative motion, not a guarantee of one identical landscape everywhere.
Several lines of evidence support plate tectonics. Earthquake locations outline active zones, ocean-floor rocks record spreading, and repeated satellite-based positioning measures motion across the surface. A mountain photograph shows shape but not its full origin or movement rate. The same landscape may also have been altered by glaciers, rivers, weathering, and human activity after tectonic processes raised or deformed it.
Three rock groups describe processes
Igneous rock forms when molten material cools and solidifies. Cooling can occur underground or after lava reaches the surface. Sedimentary rock can form from accumulated particles that become compacted and cemented, or from minerals precipitating from water; biological remains can also contribute. Weathering breaks down or chemically alters exposed rock, while erosion transports material. Deposition puts transported material down in a new setting.
rock forms when existing rock changes under heat, pressure, or chemically active fluids without completely melting. If it melts and the resulting liquid later solidifies, the new rock is igneous instead. These categories describe how material formed or changed; they do not assign every rock a required next stop. A sedimentary rock can weather back into sediment without becoming metamorphic first.
Check 1 of 3
10 pointsUse the reading above. You can try again without losing points.
Work through a decision
Reconstruct a possible route
Work through a hypothetical sequence. Lava cools into basalt. Much later, weathering loosens fragments that a river carries into a basin. The fragments are deposited, buried, and cemented. The story has moved from igneous rock to sediment and then sedimentary rock. It does not require the grains to melt during transport. Identify the process at each step rather than treating an arrow as an unexplained transformation.
Now suppose burial changes the minerals while the rock remains solid. That supplies a metamorphic step. But the written story is a model, not proof that a particular sample followed it. To test a real history, inspect textures, minerals, field relationships, and ages where available. Several samples and their locations usually tell a stronger story than an isolated stone with its context lost.
Check 2 of 3
10 pointsUse the reading above. You can try again without losing points.
Combine maps, samples, and timescales
Radar and other space-based instruments can help map surface shape. Such maps guide questions about mountain belts, drainage, and deformation, but they do not directly classify every rock or reveal its age. The photograph of mapping equipment shows how an observation is obtained, not the resulting geological interpretation. Match each claim to the measurement that can support it, from surface elevation to mineral composition.
Internal heat and gravity support tectonic processes; sunlight and gravity power much surface transport through weather and flowing water. The rock cycle connects these sources of change across very different timescales. A landslide can move material rapidly, while burial and uplift may take much longer. Draw two possible futures for one rock: weathering at the surface and alteration at depth. Explain why neither route is inevitable.
Shuttle Radar Topography Mission equipment operating from Endeavour during STS-99 in February 2000, NASA frame STS099-315-031. This is an actual photograph of the observing equipment above Earth, not a geological cross-section or an elevation map. The complete reviewed frame is preserved.
Look closely
The instrument helped map surface shape. Would that measurement alone establish how an individual rock formed?
See what to notice
Surface elevation and rock formation history are different quantities. Mapping can connect terrain and drainage, while located samples, textures, mineral measurements, and geological relationships test rock history. The photograph documents equipment used to obtain evidence; it is not itself the resulting terrain dataset.
Check 3 of 3
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Put it together
Your lesson progress
Each check connects to a part of the story. Complete all 3 to earn your 25-point lesson bonus.
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