Seafloor Spreading & Magnetic Stripes
NGSS MS-ESS2-3
Read the standard: MS-ESS2-3
Watch new ocean floor form at a mid-ocean ridge, flip Earth's magnetic poles by hand or on their real schedule, and read the mirror-image stripes left behind.
About This Interactive
What do students do?
Two panels run side by side. On the left, Earth spins with its magnetic field lines and a compass that swings around whenever the poles flip. On the right, a cross-section of a mid-ocean ridge shows magma rising from its chamber, erupting, and cooling into new crust that spreads away in both directions, colored by the field it froze in. Students set the pole flips to manual and flip them by hand, watching a new color start at the ridge and split in two, or leave them on automatic and let the field reverse on Earth's real timetable, most recently 773,000 years ago. Then they push the spreading rate from 10 to 160 millimeters a year and watch the stripes widen, both in the picture and on the graph below it. Covering the ridge with a finger and comparing the two sides makes the big idea land: the pattern is a mirror image, youngest at the ridge and older with distance, which is exactly what survey ships found across the Mid-Atlantic Ridge in the 1960s.
What does it cover?
NGSS MS-ESS2-3: analyze and interpret data on the distribution of fossils and rocks, continental shapes, and seafloor structures to provide evidence of past plate motions. Students read the stripe map as seafloor-structure data and turn its symmetry into a written argument for spreading. The worksheet grades that pattern rather than the paleomagnetism behind it, which keeps it inside the standard's assessment boundary. Automatic mode follows Earth's real polarity timetable, and stripe width equals half the spreading rate times the time between reversals, so every width students measure is a real one. Key vocabulary: mid-ocean ridge, seafloor spreading, magnetic field, magnetic pole, magnetic stripe, magma chamber.
How long does it take?
20 to 30 minutes for the quick version, or one 50 minute middle school lesson that casts the class as the crew of a 1966 survey ship puzzling over a magnetometer trace nobody on deck could explain.
What does it run on?
Every SciMinis interactive runs free in the browser with nothing to install and no accounts, on Chromebooks, laptops, tablets, and phones. It's fully bilingual: one tap switches the whole interactive, worksheet included, between English and Spanish.
What do teachers get?
Each interactive ships with vocabulary flashcards, a ten-question worksheet students can export as a PDF, and complete NGSS-aligned lesson plans: a 20 to 30 minute quick version and a full timed 5E lesson. The lesson plans and answer key stay behind a free teacher password, so students can't peek.