Final answer:
Ocean ridges and fault-block mountains are both formed by tectonic processes but differ in formation; ocean ridges at divergent boundaries and fault-block mountains via vertical crust movements. Their spreading can be assessed by comparing seafloor ages to determine rates.
Step-by-step explanation:
Ocean ridges and fault-block mountains share similarities in that they are both formed from the tectonic processes of the Earth's crust. An ocean ridge is typically formed at divergent plate boundaries, where two tectonic plates are moving apart and new crust is being formed, like the mid-Atlantic Ridge. Fault-block mountains, on the other hand, are created when large areas of the Earth's crust are broken up by faults and moved up or down relative to each other. These mountains are often associated with rifting and the extension of the Earth's crust.
While both features are the result of earth's tectonic activity, they differ in their formation and environment. Ocean ridges are underwater mountain chains formed by volcanic activity, whereas fault-block mountains occur above sea level and are formed by the movement of large crustal blocks along faults. These differences are due to the plates' interaction with each other; in the ocean ridges, the plates move apart, allowing magma to flow and create new crust, while in fault-block mountains, the crust is being stretched, causing blocks of crust to move vertically along faults, creating mountainous terrain.
Moreover, the rate at which ocean ridges spread can be determined by comparing the ages of the seafloor on either side of the ridge, such as between the mid-Atlantic Ocean and the Pacific Ocean, off the coast of South America. This age difference can show which spreading ridge is moving faster.