Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks and magma fueled by mantle convection, flows up to fill these cracks. This magma cools in the seawater to form igneous rock, a new part of Earth’s crust. This oceanic crust slowly moves away from mid-ocean ridge and the site of seafloor spreading. If the Earth's crust is continually growing, then why isn't Earth expanding? Hypothesize as to what is happening at the opposite tectonic plate boundary. Select a model that predicts the opposite boundary.

Question

Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle’s convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks and magma fueled by mantle convection, flows up to fill these cracks. This magma cools in the seawater to form igneous rock, a new part of Earth’s crust. This oceanic crust slowly moves away from mid-ocean ridge and the site of seafloor spreading. If the Earth's crust is continually growing, then why isn't Earth expanding? Hypothesize as to what is happening at the opposite tectonic plate boundary. Select a model that predicts the opposite boundary.
Responses
A	
B	
C	
D

GPT-4o mini · Answer

To understand why Earth isn't expanding despite the continuous creation of new oceanic crust through seafloor spreading at divergent plate boundaries, it's essential to consider what happens at convergent plate boundaries, which are the opposite of divergent boundaries.

At convergent plate boundaries, two tectonic plates collide, and one plate is typically forced beneath the other in a process called subduction. This leads to the formation of deep ocean trenches and volcanic arcs. As the subducted plate descends into the mantle, it is subjected to high temperatures and pressures, causing it to melt and recycle back into the mantle. This process effectively balances the creation of new crust at divergent boundaries with the removal of crust at convergent boundaries.

So, hypothesizing what is happening at the opposite tectonic plate boundary, we can conclude that while new oceanic crust is formed at divergent boundaries, the recycling of older crust at convergent boundaries (through subduction) prevents continuous expansion of Earth’s overall size.

Among the options presented (A, B, C, D), you would likely select the one that describes the subduction process at convergent plate boundaries, highlighting the recycling of crust as a mechanism that keeps Earth's size stable. However, since the actual models are not provided, I recommend selecting the one that emphasizes the role of subduction and the recycling of tectonic material.