SAT OwlQuestion bank / Text Structure and Purpose
Most people picture volcanoes as tall cones that erupt in explosive blasts. Shield volcanoes, such as Mauna Loa in Hawaii, look very different. Built up from thousands of fluid lava flows, they have broad, gently sloping sides that resemble a warrior's shield lying on the ground. Their eruptions are usually calm, with lava pouring steadily out of vents rather than bursting into the air.
Which choice best states the main purpose of the text?
To explain why explosive volcanoes are more dangerous than shield volcanoes
To argue that Mauna Loa is likely to erupt again in the near future
To compare the lava of Hawaiian volcanoes with lava from other regions
To describe a type of volcano that differs from a common image of volcanoes
Show answer and explanation
Answer: D
The text begins with the familiar picture of explosive, cone-shaped volcanoes and then describes shield volcanoes, which differ in shape and in how they erupt. Its purpose is to describe this contrasting type, as choice D says.
Choice A is tempting because the text contrasts explosive and calm eruptions, but it never discusses which type is more dangerous.
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