Along the northwestern coast of the United States the Juan de Fuca Plate is being pushed underneath the North American Plate, causing magma to rise to the surface. Magma that reaches the surface and cools will often A. erode a wide valley over time B. cause a new tectonic plate to form C. build up a mountain over time D. burn away a steep canyon.

## Step 1<br />The problem describes a geological process known as subduction, where the Juan de Fuca Plate is being pushed underneath the North American Plate. This process leads to the formation of magma.<br /><br />## Step 2<br />The magma rises to the surface and cools down. The cooling of magma leads to the formation of igneous rock.<br /><br />## Step 3<br />Over time, the accumulation of these cooled magma or igneous rock can lead to the formation of mountains. This is because the weight of the accumulated rock causes the crust to bulge upwards, leading to the formation of mountains.<br /><br />## Step 4<br />The other options, such as erosion of a wide valley, formation of a new tectonic plate, or burning away a steep canyon, are not the direct results of magma cooling and reaching the surface.