Which statements in this passage about volcanoes do not contain factual errors? The Hawaiian islands are known for their volcanic activities. In fact, the islands were formed from volcanoes. Before a volcano erupts, earthquake activity beneath the volcano decreases. Scientists use seismometers to measure the earthquake activity that occurs beneath a volcano. They then predict the eruption of that volcano. When a volcano erupts, the amount of carbon dioxide and sulfur dioxide emitted decreases. Scientists measure the amount of these gases to determine the amount of magma present in the volcanic reservoir.