About Hawaii: “Loveliest Fleet of Islands Anchored in any Ocean” Where do the islands come from? Why do they form? How do they form? (V1)

Hawaiian Archipelago  Chain of islands that strikes NW - SE across the northern Pacific Ocean  3000 km from nearest continent & 800 km from nearest island  Each island is the summit of a great volcano that rises form sea floor  And is part of a great undersea mountain range. Hawaiian Ridge & Emperor Seamounts

Hawaiian Ridge  NW Hawaiian Islands - Kure to Nehoa Flat or LOW Islands - coral & agal reefs Flat or LOW Islands - coral & agal reefs 1750 km long & 5000 m above the sea floor 1750 km long & 5000 m above the sea floor Older than 6 million years Older than 6 million years  SE Hawaiian Islands - Kauai to Hawaii Volcanic or HIGH islands - volcanoes Volcanic or HIGH islands - volcanoes 650 km long & up to 4000 m above sea level 650 km long & up to 4000 m above sea level (what does this mean for total height?)(what does this mean for total height?) Younger than 6 million years Younger than 6 million years Located between Lat N & Lon W Located between Lat N & Lon W

Hawaiian-Emperor chain

Main Islands & Volcanoes Oldest to Youngest  Kauai - Kauai  Niihau - Niihau  Oahu - Waianae & Koolau  Molokai - W & E Molokai  Lanai - Lanai  Maui - W. Maui & Haleakala  Hawaii -Kohala, Mauna Kea, Hualalai, Mauna Loa & Kilauea  Loihi

Ages of volcanoes in m.y.

Now, the question is  Where do these volcanoes come from?  We know that most of the volcanoes & earthquakes are located at plate margins!  AND  Hawaii is located in the middle of the Pacific Ocean, far from any plate boundary!  So, how come volcanoes, earthquakes???

HOT SPOTS!!!

HOT SPOTS! WHAT ARE HOT SPOTS? Hot Spots - deep, long-lived, mostly stationary mantle magma sources Expressed at the surface by: linear chain of volcanoes that age with distance from hot spot Over 100 identified Used as fixed points against which plate motion is measured

Global distribution of Hot Spots

Where do Hot Spots come from?  Are thought to result from mantle plumes hot, buoyant rock rising from the deep mantle hot, buoyant rock rising from the deep mantle plumes melt when they approach the surface plumes melt when they approach the surface  Origin of mantle plumes is not known may come from as deep as the core-mantle boundary may come from as deep as the core-mantle boundary or made of recycled subducted plates?? or made of recycled subducted plates??

Plate Tectonics & Hot Spots

Hot Spot Traces  Long chains of volcanoes with an age progression along their length  Occur on both oceanic and continental lithosphere  Form as plates move over a fixed magma source in the mantle  Therefore, they record plate motion relative to the mantle

Hawaiian-Emperor chain

Location of the various islands over the hot spot (red circle) at different times

A Quick Review of Island Formation Islands form over a “hot spot” in the mantle then move away riding the Pacific Plate Results in a chain of islands with an age progression along its length {Responsible for different magma types in different life stages, or whether there is any magma available at all} - w hen magma supply is low, erosion dominates shaping the landscape

Homework #1: How fast does the Pacific Plate move over the Hawaiian Hot Spot?

L2 & L3