Question

1. describe how the pattern of magnetic field reversal of ocean floor basalt shown in the rocks on either side of the juan de fuca ridge is evidence for convection currents in the mantle.

Explanation:

1. As mantle convection currents move tectonic plates apart at the Juan de Fuca Ridge, magma rises to form new ocean floor basalt.
2. As this basalt cools, iron-rich minerals align with Earth's current magnetic field, locking in that magnetic orientation.
3. Earth's magnetic field reverses periodically over geologic time. Each reversal creates a new band of basalt with the opposite magnetic alignment as it forms at the ridge.
4. The resulting magnetic bands are symmetrical on either side of the ridge: new rock forms at the ridge, and older rock is pushed outward in both directions. This mirror pattern confirms that ocean crust is created at the ridge and moved away by mantle convection, with each band recording a past magnetic reversal.

Answer:

The symmetrical pattern of magnetic reversals in basalt on either side of the Juan de Fuca Ridge supports mantle convection currents as follows:

• Magma rises at the ridge (driven by convection) and cools, locking in Earth's current magnetic orientation in its iron minerals.
• When Earth's magnetic field reverses, new basalt forming at the ridge records the reversed orientation.
• The crust created at the ridge is pushed outward in both directions by ongoing convection, creating matching, mirrored magnetic strip patterns on each side of the ridge. This symmetry proves ocean floor is generated at the ridge and moved by mantle convection, with each strip marking a past magnetic reversal event.