Chapter 8: Earthquakes and Volcanoes Section 3: Earthquakes, Volcanoes, and Plate Tectonics

A. Earth’s crust is broken into plates that move around.

B. Most volcanoes form where plates are colliding or moving apart. Divergent plate boundaries – where plates move apart

1. Divergent plate boundary Long cracks called rifts form between them. Fissure eruptions are common where plates separate.

2. Convergent plate boundaries – where plates collide and denser plates subduct, or are forced underneath less dense plates

3. Hot spots – large rising bodies of magma force their way through the Earth’s crust, not at plate boundaries

C. Most earthquakes occur where plates are colliding or moving apart

Lo’ihi: Island Under Construction Lo`ihi Seamount is an active volcano built on the seafloor south of Kilauea about 30 km from shore (off the coast of The Big Island)

Lo’ihi is currently in a stage between pre-shield volcano and shield volcano