Page 411 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 12 The Dynamic Planet 375
▲Figure 12.23 Tamu Massif, the largest volcano on earth. This image of the seafloor shows the shape and size of Tamu Massif in the northern Pacific Ocean. Mauna Loa in Hawai‘i is higher than Tamu Massif above the seafloor, but is much smaller in overall area. [Image courtesy of Will Sager.]
A new addition to the Hawaiian chain is still a sea- mount. It rises 3350 m from its base, but is still 975 m be- neath the ocean surface. Even though this new island will not experience the tropical Sun for about 10000 years, it is already named Lo’ihi (noted on the map).
Iceland is another island that results from an active hot spot, this one sitting astride a mid-ocean ridge. It is an excellent example of a segment of mid-ocean ridge rising above sea level. This hot spot continues to gener- ate eruptions from deep in the mantle, the most recent occurring in 2010 and 2011. As a result, Iceland is still growing in area and volume.
In 2013, scientists confirmed that the Tamu Massif, located above a hot spot in the Pacific Ocean about 1600 km east of Japan, is the largest volcano on Earth, and one of the biggest in the solar system (Figure 12.23). Part of the Shatsky Rise, a massive undersea volcanic plateau similar in size to California, the Tamu Massif covers about 310 800 km2, an area far larger than Mauna Loa on Hawai‘i, covering only 5200 km2. Until recently, scientists thought Tamu Massif was a composite of smaller volcanic structures, formed in a similar man- ner as the island of Hawai‘i. However, recent research determined that this feature is composed of related ma- terials, formed some 145 m.y.a. above a hot spot that coincides with the boundaries of three tectonic plates.
The form and processes of this undersea feature are fur- ther evidence that, indeed, Earth is a dynamic planet.
The Geologic Cycle
We see in this chapter that Earth’s crust is in an ongo- ing state of change, being formed, deformed, moved, and broken down by physical and chemical processes. While the planet’s endogenic (internal) system is at work build- ing landforms, the exogenic (external) system is busily wearing them down. This vast give-and-take at the Earth– atmosphere–ocean interface is summarized in the geologic cycle. It is fuelled from two sources—Earth’s internal heat and solar energy from space—while being influenced by the ever-present leveling force of Earth’s gravity (see Geo- systems in Action, Figure GIA 12).
The geologic cycle is itself composed of three prin- cipal cycles—the hydrologic cycle, which we summa- rized in Chapter 9, and the rock and tectonic cycles covered in this chapter. The hydrologic cycle works on Earth’s surface through the exogenic processes of weathering, erosion, transportation, and deposition driven by the energy–atmosphere and water–weather systems and represented by the physical action of water, ice, and wind. The rock cycle produces the three basic rock types found in the crust—igneous, metamor- phic, and sedimentary. The tectonic cycle brings heat energy and new material to the surface and recycles surface material, creating movement and deformation of the crust.
CrITICalthinking 12.3
How Fast Is the Pacific Plate Moving?
Tracing the motion of the Pacific plate shown in Figure 12.22 (note the map’s graphic scale in the lower-left corner) reveals that the island of Midway formed 27.7 m.y.a. over the hot spot that today is active under the southeast coast of the big island of Hawai‘i. Use the scale of the map to roughly deter- mine the average annual speed of the Pacific plate in centi- metres per year for Midway to have travelled this distance. given your calculation for the plate speed and assuming the directions of movement remain the same, approximately how many years will it take the remnants of Midway to reach 50° n in the upper-left corner of the map? •
Georeport 12.5 The largest volcano on Earth
In 2013, scientists confirmed that the Tamu Massif, located in the Pacific Ocean about 1600 km east of Japan, is the
largest volcano on Earth and one of the biggest in the solar system. Part of the Shatsky rise, a massive undersea volcanic plateau similar in size to California, the Tamu Massif covers about 310800 km2, an area far larger than Mauna Loa’s 5200 km2 on Hawai‘i. Until recently, scientists thought Tamu Massif was a composite of smaller volcanic structures, formed in a manner similar to that of the island of Hawai‘i. However, recent research determined that this feature is composed of related materials, formed some 145 m.y.a. above a hot spot that coincides with the boundaries of three tectonic plates. More information is at geology.com/records/ largest-volcano/.