Juan de Fuca is one of the plates that slide under the continental North American plate causing the convergence.
Volcanic eruptions near the oceanic lithosphere contributed to the formation of the Cascades and Andean-type mountains. This was because of the subduction of the landscape along the mountains that led to the invasion of magma from the layer and some due to crustal reduction. It is apparent that at the boundaries of the ranges are sedimentary rocks that slant, forming hogbacks. When the molten rocks and solids present under the earth mix together, then they form the magma. This substance is capable of triggering intrusion into the adjacent rocks that form the sills. The magma rocks are formed when explosive gases and hot underground water melt the glacial ice near the mantles (Price 24).
The magma at Mt. St. Helens contains glacial rocks, ash and sedimentary rocks that melt during eruptions to form the mountain. This happens when the pressure pushed up the weaker sedimentary rocks that mix with the ash along the mantes (Foxworthy and Hill 23). The eruption can take long hours in the atmosphere before reaching the surface and this is harmful to the people in the vicinity. The magma erupted through the explosives are highly viscous and resistant to flow, which make the steep volcanoes. As a result, the chemical investigation of the eruptive materials from various phases of Mount St. Helens volcanism indicates that the magmatic structure interacts with different chemicals such as silicic and other compounds (Anderson 50).
The Andean-type mountains extend from the Columbian to the Chilean regions. They were shaped through the subduction of the Nazca plates that collided with the Antarctic plates to cause an eruption. In this regard, the other geologic features associated with the Andean-Type mountains entail faults, folds and igneous rocks (Price 24). These features are remnants of active eruptions