WA3 geog

What is the difference between continental crust and oceanic crust?

Continental crust makes up the land masses, while oceanic crust makes up the seafloor. Oceanic crust is denser than continental crust.

Slab pull force

When two plates converge, the denser oceanic crust is pulled down by gravity as it subducts beneath the less dense crust. The denser oceanic crust sinks deeper into the mantle under its own weight, pulling the rest of the plate with it, contributing to further convergence.

How does the age of rocks support tectonic plate theory

Since the age of the rocks is youngest nearer to the mid-ocean ridge and gets progressively older further away, it shows that new crust is being formed at the divergent boundary as magma rises from the mantle. As seafloor spreading continues, older rocks are pushed away from the ridge, creating a symmetrical pattern of younger rocks near the ridge and progressively older rocks farther away. This lateral movement highlights the fact that the tectonic plates are in constant motion due to seafloor spreading, thus supporting plate tectonic theory.

Describe the magnetic striping thing on the seafloor

Magnetic striping is the zebra-like pattern where there are strips of normal polarity rocks alternating alongside strips of reversed polarity rocks on the seafloor.

How does magnetic striping support the plate tectonic theory?

The zebra-like pattern is symmetrical on both sides of the mid-ocean ridge, showing that it is not a random or isolated occurrence. As magma rises at the ridge, it cools and solidifies to form new oceanic crust. The iron-rich minerals in the basalt align with Earth's magnetic field and record its polarity at the time of cooling. When Earth's magnetic field reverses, newly formed crust records the opposite polarity, creating alternating stripes of normal and reversed polarity. Over millions of years, this process produces symmetrical magnetic stripes on either side of the ridge. This supports the Plate Tectonic Theory, as it shows that new crust is continuously formed at the mid-ocean ridge and moves away in opposite directions through seafloor spreading.