Why is molten lava often covered with zig-zag patterns?

Asked by: Anonymous

The seething lakes of lava formed during volcanic eruptions are often covered with distinctive zig-zag patterns, with the searing-hot lava showing up below a darker crust. Using a combination of theory and experiments with molten wax, American geophysicists have shown that the angle of the zig-zags is determined by the rate at which fresh lava spreads out, and how quickly it subsequently cools and turns solid.

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