Evidence for moving plates

Moving plates were discovered by fitting many clues together. A coastline match alone is weaker evidence than patterns that agree across rocks and oceans.

Lesson 1 of 33 parts Practice Flashcards

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Continental fit and Fossil correlation

Objective: Explain continental fit and fossil correlation, distinguish their meanings, and apply them to a described case.

Continental fit: Corresponding continental margins helped motivate continental-drift hypotheses but are not sufficient evidence alone. Fossil correlation: Matching fossils on separated landmasses can support former geographical connections. Scientific acceptance of plate motion depended on converging observations and a workable mechanism, rather than a single visual resemblance. Magnetic stripes and age patterns constrain how ocean crust forms and moves. Fossils and rock sequences provide independent geological context. Satellite measurements track current motion but do not alone reconstruct every ancient position. Strong interpretations explain several observations with a consistent account of the processes involved. Application: A class compares the continental shelves on opposite Atlantic margins. This most directly illustrates continental fit. Similar land-organism fossils occur across an ocean gap. This most directly illustrates fossil correlation.

Worked examples

Try itOriginal teaching scenario: A class compares the continental shelves on opposite Atlantic margins. Which idea from this section does it most directly illustrate?Show answer

Step 1 — Read the observation: A class compares the continental shelves on opposite Atlantic margins. Step 2 — Recall the relevant idea: Corresponding continental margins helped motivate continental-drift hypotheses but are not sufficient evidence alone. Step 3 — Connect the observation to the idea: The scenario is an illustration of continental fit. Step 4 — Check the limit: This short scenario illustrates the concept; it does not establish every detail or exclude every other influence in a real situation.

Try itOriginal teaching scenario: Similar land-organism fossils occur across an ocean gap. Which idea from this section does it most directly illustrate?Show answer

Step 1 — Read the observation: Similar land-organism fossils occur across an ocean gap. Step 2 — Recall the relevant idea: Matching fossils on separated landmasses can support former geographical connections. Step 3 — Connect the observation to the idea: The scenario is an illustration of fossil correlation. Step 4 — Check the limit: This short scenario illustrates the concept; it does not establish every detail or exclude every other influence in a real situation.

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Continental fit and Fossil correlation

Objective: Explain continental fit and fossil correlation, distinguish their meanings, and apply them to a described case.

Worked examples

Try itOriginal teaching scenario: A class compares the continental shelves on opposite Atlantic margins. Which idea from this section does it most directly illustrate?Show answer

Try itOriginal teaching scenario: Similar land-organism fossils occur across an ocean gap. Which idea from this section does it most directly illustrate?Show answer

Seafloor spreading and Magnetic stripes

Objective: Explain seafloor spreading and magnetic stripes, distinguish their meanings, and apply them to a described case.

Seafloor spreading: New oceanic crust forms at spreading ridges and moves away as plates diverge. Magnetic stripes: Symmetrical magnetic patterns record reversals as oceanic crust forms and spreads. Scientific acceptance of plate motion depended on converging observations and a workable mechanism, rather than a single visual resemblance. Magnetic stripes and age patterns constrain how ocean crust forms and moves. Fossils and rock sequences provide independent geological context. Satellite measurements track current motion but do not alone reconstruct every ancient position. Strong interpretations explain several observations with a consistent account of the processes involved. Application: Young basalt occurs near an ocean ridge. This most directly illustrates seafloor spreading. Matching magnetic bands appear on both sides of a ridge. This most directly illustrates magnetic stripes.

Worked examples

Try itOriginal teaching scenario: Young basalt occurs near an ocean ridge. Which idea from this section does it most directly illustrate?Show answer

Step 1 — Read the observation: Young basalt occurs near an ocean ridge. Step 2 — Recall the relevant idea: New oceanic crust forms at spreading ridges and moves away as plates diverge. Step 3 — Connect the observation to the idea: The scenario is an illustration of seafloor spreading. Step 4 — Check the limit: This short scenario illustrates the concept; it does not establish every detail or exclude every other influence in a real situation.

Try itOriginal teaching scenario: Matching magnetic bands appear on both sides of a ridge. Which idea from this section does it most directly illustrate?Show answer

Step 1 — Read the observation: Matching magnetic bands appear on both sides of a ridge. Step 2 — Recall the relevant idea: Symmetrical magnetic patterns record reversals as oceanic crust forms and spreads. Step 3 — Connect the observation to the idea: The scenario is an illustration of magnetic stripes. Step 4 — Check the limit: This short scenario illustrates the concept; it does not establish every detail or exclude every other influence in a real situation.

Ocean-crust ages and Geodetic measurement

Objective: Explain ocean-crust ages and geodetic measurement, distinguish their meanings, and apply them to a described case.

Ocean-crust ages: Oceanic crust generally becomes older with increasing distance from a spreading ridge. Geodetic measurement: Satellite-based measurements directly track present-day surface motion. Scientific acceptance of plate motion depended on converging observations and a workable mechanism, rather than a single visual resemblance. Magnetic stripes and age patterns constrain how ocean crust forms and moves. Fossils and rock sequences provide independent geological context. Satellite measurements track current motion but do not alone reconstruct every ancient position. Strong interpretations explain several observations with a consistent account of the processes involved. Application: Samples farther from a ridge have older formation ages. This most directly illustrates ocean-crust ages. Repeated position measurements reveal a plate moving centimeters per year. This most directly illustrates geodetic measurement.

Worked examples

Try itOriginal teaching scenario: Samples farther from a ridge have older formation ages. Which idea from this section does it most directly illustrate?Show answer

Step 1 — Read the observation: Samples farther from a ridge have older formation ages. Step 2 — Recall the relevant idea: Oceanic crust generally becomes older with increasing distance from a spreading ridge. Step 3 — Connect the observation to the idea: The scenario is an illustration of ocean-crust ages. Step 4 — Check the limit: This short scenario illustrates the concept; it does not establish every detail or exclude every other influence in a real situation.

Try itOriginal teaching scenario: Repeated position measurements reveal a plate moving centimeters per year. Which idea from this section does it most directly illustrate?Show answer

Step 1 — Read the observation: Repeated position measurements reveal a plate moving centimeters per year. Step 2 — Recall the relevant idea: Satellite-based measurements directly track present-day surface motion. Step 3 — Connect the observation to the idea: The scenario is an illustration of geodetic measurement. Step 4 — Check the limit: This short scenario illustrates the concept; it does not establish every detail or exclude every other influence in a real situation.

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