the mountainous west, the Great Plains, the Canadian Shield, the varied eastern region, and the Caribbean. Which of these is an isthmus? What two larger areas of land does this isthmus connect?

a mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. this uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.a geomagnetic reversal is a change in a planet's magnetic field such that the positions of magnetic north and magnetic south are interchanged.