Ohio Assessment for Educators (OAE) Integrated Science (024) Practice Exam

What type of volcanic rock is produced primarily by shield volcanoes?

1. Basalt

2. Andesite

3. Rhyolite

4. Dacite

The correct answer is: Basalt

Shield volcanoes are characterized by their broad, gentle slopes and are primarily formed by the eruption of low-viscosity basaltic lava. This type of lava can flow over long distances, allowing for the formation of the wide, shield-like shape typical of these volcanoes. The predominant rock type produced from shield volcanoes is basalt, which is a mafic rock rich in iron and magnesium and has a relatively low silica content compared to other volcanic rocks. This low viscosity enables the lava to escape easily during eruptions, resulting in the gradual buildup of extensive, flattened volcanic structures that define shield volcanoes. The other types of volcanic rocks mentioned — andesite, rhyolite, and dacite — are typically associated with more explosive volcanic activity and higher silica content, which contribute to their higher viscosity and the stratovolcano structures they typically form.