MAGNETIC STRIPING & SEA FLOOR SPREADING

MAGNETIC STRIPING & SEA FLOOR SPREADING Core science (explain in THIS order) ● Magma rises at mid-ocean ridges → cools → forms new oceanic crust ● As it cools, iron particles in the rock line up with Earth's magnetic field at that time ● Earth's magnetic field flips polarity (N/S swap) every so often over time ● New crust keeps forming at the ridge and pushes older crust outward → creates matching stripes of "normal" and "reversed" polarity on both sides of the ridge Why this proves plate tectonics ● Stripes are symmetrical on both sides → shows crust is made at the ridge and moves apart in both directions = sea floor spreading ● Stripes get older the further out you go → shows direction + speed of plate movement ● It's basically a "recording" of magnetic history in the rock → lets scientists measure/date plate movement, not just guess 🎯 HOW TO ANSWER IN EXAM 1. Explain how it forms first — magma rises, cools, minerals line up ○ ⚠ Don't skip this and jump straight to "proves plates move" 2. Name the pattern — symmetrical, alternating stripes either side of ridge 3. Link back to theory — say this proves new crust keeps forming at ridges and spreads outward ⚠ For "explain" questions ● Need BOTH: describe the pattern + link it to spreading/movement ● Just describing the stripes (they exist, they alternate) without saying "this proves plates are moving apart" = won't get full marks