Question

what plate movements cause valcanos

Answer 1

You probably mean "volcanoes." The main plate movements that produce volcanoes are:

- Divergent boundaries (plates move apart)
- Effect: mantle rises and melts by decompression.
- Where: mid-ocean ridges (Mid‑Atlantic Ridge) and continental rifts (East African Rift).
- Typical volcanism: basaltic, relatively fluid eruptions, fissure eruptions and shield-type volcanism.

- Convergent boundaries / subduction zones (plates move together)
- Effect: one plate sinks (subducts) into the mantle, releases water and other volatiles that lower the melting temperature of the overlying mantle → magma forms.
- Where: oceanic‑continental or oceanic‑oceanic subduction zones (e.g., the Pacific "Ring of Fire," Andes, Japan, Cascades).
- Typical volcanism: more silica‑rich magmas (andesite/rhyolite), often explosive stratovolcanoes.

- Transform boundaries (plates slide past each other)
- Effect: generally do not produce much volcanism because there’s little upwelling or subduction; local extension or fractures can sometimes allow small eruptions, but volcanism is uncommon.

- Intraplate hotspots (not a plate boundary movement but important)
- Effect: mantle plumes or local upwellings produce melting beneath a moving plate.
- Where: inside plates, producing chains of volcanoes (Hawaii) or large volcanic provinces (Yellowstone).
- Typical volcanism: usually basaltic shield volcanoes for oceanic hotspots; continental hotspots can produce explosive eruptions and calderas.

Key melting mechanisms: decompression melting (at divergent ridges and rising plumes), flux melting (water-driven at subduction zones), and heat-transfer melting (from hot mantle plumes). Different settings also produce different magma chemistry and eruption styles.

If you want, I can give diagrams, map examples, or explain why subduction makes eruptions more explosive.