Buchanan, who is buried in Lancaster, has regularly been ranked one of the worst presidents by historians, citing his ambivalence towards the South wanting to secede from the Union prior to the Civil War.
A shield volcano is a type of volcano usually built almost entirely of fluid magma flows. They are named for their large size and low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from stratovolcanoes.
Others are formed when the summit of a volcano collapses into an empty magma cavern that had stored the magma prior to eruption. Shield Volcanoes. Shield volcanoes, formed when large flows of lava spread rapidly from central vents or rows of vents, are the largest volcanoes.Because the lava moves rapidly and spreads out in a broad area, it does not form a tall, steep cone. Instead, shield volcanoes are dome-shaped mountains with broad bases and gentle slopes.tratovolcanoes, or composite volcanoes, get their name from the different layers, or strata, of ash and lava that form them. Most stratovolcanoes are irregularly shaped mountains formed by material ejected from both a central vent and other vents on the sides of the mountain.