Here's a breakdown of why:
* Seafloor Spreading: Mid-ocean ridges are where new oceanic crust is created. Magma rises from the mantle, erupts, and cools to form basalt. This process, known as seafloor spreading, pushes older crust further away from the ridge.
* Age Gradient: As a result, the basalt closest to the ridge is the youngest, and the basalt further away is progressively older. This age gradient is a strong piece of evidence supporting the theory of plate tectonics.
* Magnetic Stripes: Additionally, the orientation of magnetic minerals within the basalt aligns with the Earth's magnetic field at the time of formation. These magnetic stripes, which are symmetrical on either side of the ridge, further confirm the age progression and seafloor spreading.
In summary, the observation of increasing age in basalt away from a mid-ocean ridge provides strong evidence for seafloor spreading and the continuous creation of new oceanic crust.
