The Hawaiian volcanic islands stretch across the Pacific beneath scattered white clouds in an ISS photograph.

Loading photograph

Preparing the 3D view

Preparing lighting and the first complete frame…

Model scale

Independent hotspot sections. age direction is geographic. geometry not to scale.

Select Hawaiʻi, Yellowstone or both to compare their volcanic tracks.

How to read these results

Each section shows the plate moving over a fixed thermal anomaly, without an assigned travel rate. Right is northwest for Hawaiʻi and southwest for Yellowstone.

Hotspots

Use the direction of increasing volcanic age to infer relative plate motion in the Hawaiian and Yellowstone examples.

Drag to rotate. Hold Ctrl and scroll to zoom, or pinch on a touch screen.

Why it happens

A moving plate can carry older volcanoes away from a long-lived region of melting. Comparing the direction of increasing age along a volcanic track helps explain relative plate motion.

Loading photograph

Hawaii from the ISS. The volcanic chain records Pacific plate motion relative to a long-lived hotspot; the youngest main island is at the southeast end.

Try a comparison

Enable Yellowstone and compare its different geographic age direction.

Reading the result

The sections illustrate motion and age direction; they do not calculate eruption dates or reproduce the full structure of a mantle plume.

A common misunderstanding

A hotspot must remain perfectly fixed while its plate moves.

A volcanic age track records motion of a plate relative to a region of melting. Plate motion is important, but the source can also shift as the mantle moves. Track direction and age therefore constrain relative motion without requiring an exactly stationary source.

Cases

Exam language

Hotspot

A region of persistent volcanism that can occur within a plate or at a boundary. Many hotspots are associated with mantle upwelling; not all have an established deep plume origin.

Loading photograph

Hawaii from the ISS. The volcanic chain records Pacific plate motion relative to a long-lived hotspot; the youngest main island is at the southeast end.

Seamount

An underwater mountain, usually volcanic. Seamounts need not lie on an age-progressive hotspot chain or have once stood above sea level.

Loading photograph

NOAA multibeam survey of an Arctic seamount. A seamount is a submarine mountain; a guyot is the flat-topped subtype. Surveyed topography, rather than colour alone, is needed to distinguish them.

Mantle plume

An upwelling of unusually hot mantle material that may supply hotspot volcanism. It is mostly deforming solid rock, with partial melting possible near the top.

Caldera

A large volcanic depression formed mainly when the ground collapses into an underlying magma reservoir after magma is withdrawn.

Loading photograph

USGS aerial photograph of Crater Lake, Oregon. Collapse following the eruption of Mount Mazama formed the caldera; Wizard Island is a younger volcanic cone.

Age-progressive chain

Volcanoes that get older away from the active centre, recording plate motion.

Intraplate volcanism

Volcanic activity occurring within a tectonic plate rather than along its boundary. Hawaiʻi is one example. Possible causes include mantle upwelling and lithospheric processes; its location alone does not establish the depth or structure of the magma source.

Partial melt

Melting of only part of a rock, because its constituent minerals do not all melt under the same conditions. Melt may separate and rise while solid material remains. This helps explain why magma differs in composition from its source rock.

Loading photograph

Mantle peridotite enclosed in volcanic host rock at Peridot Mesa, Arizona. It is physical evidence of rock from the upper mantle. The mantle is predominantly solid; local partial melting is not a global magma ocean.

Guyot

A submerged seamount with a relatively flat summit, commonly formed when a volcanic island is eroded near sea level and later subsides.

Process0.40