Seafloor Spreading Centers: The Life Cycle of the Seafloor
Lesson Plan by Ashlee Henig and Stephen Halpern

This 9 block-day lesson plan leads students through the discovery of Plate Tectonics in much the same way scientists learned about it in the 1960’s. Beginning with early evidence of continental drift such as the fit of landmasses and matching fossil records bridging continents, to understanding the features of the seafloor, and discovering the symmetric pattern of seafloor magnetic stripes and ages, students will piece together the evidence pointing from Continental Drift to seafloor spreading and finally to the unified theory of Plate Tectonics. This unit climaxes with the concepts of seafloor formation and destruction, emphasizing process of seafloor spreading and the cause of the Pacific “Ring of Fire”.
  • Students will learn the features of the seafloor that provide evidence for seafloor spreading and plate tectonics and how those features formed.
  • Students will practice reasoning through evidence to draw conclusions.
  • Students will learn the processes of creation and destruction of the seafloor.
  • Students will learn land features associated with plate tectonics, and seafloor spreading in particular.
  • Students will learn about the Ring of Fire and its destructive hazards to coastal areas.
  • The Seafloor is flat or shaped like a bowl. The deepest part of the seafloor is in the middle of the ocean.
  • The seafloor is as old as the continents.
  • The entire seafloor is the same age.
  • The Earth is expanding.
  • Seafloor is never destroyed.
  • Continents float on water.
  • Day 1: Exploring Continent Drift.
  • Day 2: Seafloor Shape and Features.
  • Day 3-4: Patterns on the Seafloor: Magnetic Stripes.
  • Day 5: Patterns on the Seafloor: Seafloor Ages.
  • Day 6-7: Seafloor Spreading.
  • Day 8: Subduction and the “Ring of Fire”.
  • Day 9: Review and exam.
  • This unit is designed for use in a High School Earth Science or Marine Science classroom.
  • It is approximately a 9 day unit, and while it is ideal to teach the lessons as a series, some lessons can be used individually.
  • Prerequisites for this unit include knowledge of division and plotting graphs, the ability to recognize patterns, and 6th grade knowledge of plate tectonics.
  • When taught in series, the lessons proceed in much the same way that scientists discovered seafloor spreading and plate tectonics.
  • Alternatively, this lesson can be taught after the concept of seafloor spreading so the evidence can be put into context. This choice is left up to the teacher depending on the reasoning skills of the students.
  • Assessment of understanding is primarily based on daily worksheets that require students to apply the concepts they have learned or to use their prior knowledge to reason through a problem.
  • An optional pop-quiz and a formal unit exam serve to gauge overall understanding and retention of information.
  • The idea of Continental Drift and its supporting and refuting evidence is addressed.
  • A worksheet asks students to decipher between factual evidence and non-evidence.
  • Students use their knowledge of the supporting evidence to assemble a puzzle-map of Pangea from the individual continents.
  • The unit begins by teaching students the methods used by scientists to study the seafloor.
  • Various seafloor features are presented.
  • Students perform a mapping and graphing activity meant to familiarize them with the range of depths and features on the seafloor.
  • A day is used to teach students about the Earth’s magnetic field through the lesson plan and activities from the 2010 SCC Solid Earth and Plate Tectonics Unit (week 1, day 4). Additional information is available in this unit’s lesson plan.
  • Students then discover the symmetric pattern in magnetic stripes on either side of the oceanic ridges by plotting the polarity of various rock samples.
  • Lectures familiarize students with the background information of oceanic crustal ages determined by scientists studying the seafloor.
  • Students follow the steps of scientists to uncover the symmetric pattern observed in the ages by correlating rock age and location on a map.
  • In this part of the unit, students synthesize the information they have learned about patterns in the seafloor and evidence of Continental Drift to arrive at the conclusion that the seafloor is spreading.
  • An associated lecture will explain the process of seafloor spreading in detail and solidify key points.
  • Students will observe “seafloor” spreading in the classroom through a paper towel spreading center demonstration illustrating the relative motion of the plates.
  • A worksheet will then test for understanding and introduce global earthquake distribution as an indicator of plate movements. Emphasis is put on the “non-spreading center” earthquakes and their significance.
  • A lecture will pose the question to students: Is the Earth growing? Subduction is introduced as the method of seafloor destruction.
  • Students construct a paper model spreading center with and without subduction and discuss the differences between the Pacific and Atlantic Oceans.
  • As a partial review, students watch a video and answer questions on the Ring of Fire.
  • The final day is intended for review and the unit assessment.

Seafloor Magnetic Stripes


Global Seafloor Spreading Centers


Creation and Destruction
of Oceanic Crust
Lesson Specifics
  • Grade Level: High School Earth Science or Marine Science classroom.
  • Time Frame: 9 days.
  • Science Standards: "This unit particularly emphasizes California State Science Standard 3a. Science standards also addressed by this unit include portions of 3b, 3e, and 3f."
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Roger Revelle
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