Mid Ocean Ridge
In the 1960s hidden chains of volcanoes were discovered under the sea. At these Mid Ocean Ridges or constructive margins oceanic crust is created at chains of volcano which form the boundary between two plates. As new crust is formed the older crust is pushed away a process known as sea floor spreading.
The iron minerals in the basaltic lava align with changes in the earths magnetic field creating magnetic "stripes". Pillow lavas are erupted forming ocean floor,these are fed by an extensive network of dykes fed by gabbroic magma chambers. To see these characteristics on land you need to find an ophiolite , a slice of oceanic crust which has thrust onto the land. The Lizard Peninsula in Cornwall or the Troodos Ophiolite in Cyprus.