(a) What would be the average rate of movement of the...

(a) What would be the average rate of movement of the Pacific Plate according to the hot-spot model? (b) Assuming that a constant rate of movement has been maintained, what is the approximate age of the northern end of the $1900 \mathrm{~km}$-long Emperor Chain? (c) Suggest a reason for the kink in the chain as a whole (at the western end of the Hawaiian sector, the southern end of the Emperor sector). (d) In fact, the age of the northern end of the Emperor Chain has been dated at about $72 \mathrm{Ma}$. Assuming that a change in rate of plate motion coincided with the change in direction of motion you have just postulated, what was the average rate of movement of the Pacific Plate between 72 and 43 Mago?

(a) What would be the average rate of movement of the Pacific Plate according to the hot-spot model?
(b) Assuming that a constant rate of movement has been maintained, what is the approximate age of the northern end of the $1900 \mathrm{~km}$-long Emperor Chain?
(c) Suggest a reason for the kink in the chain as a whole (at the western end of the Hawaiian sector, the southern end of the Emperor sector).
(d) In fact, the age of the northern end of the Emperor Chain has been dated at about $72 \mathrm{Ma}$. Assuming that a change in rate of plate motion coincided with the change in direction of motion you have just postulated, what was the average rate of movement of the Pacific Plate between 72 and 43 Mago?

Key Concepts

Geochronology

Geochronology is the branch of geology focused on dating rocks, fossils, and events. By assigning ages to rock sequences and volcanic formations, it allows scientists to calculate the timing of tectonic processes, such as changes in plate motion, and provides temporal constraints that are essential for understanding the evolution of volcanic chains and other geological features.

Plate Motion Reorientation

Plate motion reorientation refers to the phenomenon where the direction of a tectonic plate's movement changes over time. Such reorientations can be recorded as kinks or bends in volcanic chains. Analyzing these changes helps geoscientists understand shifts in the driving forces of plate tectonics, likely due to changes in mantle convection patterns or interactions with neighboring plates.

Plate Tectonics

Plate tectonics is the scientific theory that Earth's outer shell is divided into several plates that move over the more fluid asthenosphere beneath them. This movement is responsible for a range of geological phenomena including earthquakes, volcanic activity, and the creation of mountain ranges. Understanding plate interactions helps explain the formation and evolution of various geological structures.

Hotspot Model

The hotspot model involves a relatively stationary source of magma (often attributed to a mantle plume) that creates volcanic activity as a tectonic plate moves over it. This model explains the formation of linear volcanic chains by demonstrating that the fixed location of the hotspot, amid a moving plate, leaves a trail that records the direction and rate of plate motion over geological time.

Rate of Plate Motion

The calculation of plate motion involves determining the average speed at which a tectonic plate moves by dividing the distance traveled by the time over which the movement occurred. This concept is crucial when reconstructing the history of volcanic chains or other features that provide a record of a plate's motion across a hotspot.

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