 Accretionary prisms form due to what process? subduction divergence rifting transform motionAs sediment on the down going slab is scraped off by the overriding plate during subduction, anaccretionary prism forms. SEC: 2.8, Figure 2.22a Asthenosphere is warm enough to flow slowly. subducts when it collides with continental lithosphere. is the lower layer of both continental and oceanic lithosphere. is the uppermost layer of Earth's core.Asthenosphere is part of the mantle, not the core. It supports the lithosphere, rather than beingpart of it or colliding with or subducting under it. SEC: 2. Choose the FALSE statement. Magnetic anomalies are places where the magnetic field strength is either greater or less than the expectedstrength. termed normal if the atomic dipoles match Earth's current magnetic field and pointfrom north to south. found only on the seafloor. measured with an instrument called a magnetometer.Magnetic anomalies are found on continents as well as on the seafloor. They create irregularpatterns on continents and distinct alternating bands on the seafloor. SEC: 2.5, Figure 2.10 Earth's magnetic field is created by flow of liquid iron in Earth's molten outer core. centrifugal force pushing on Earth's crust. convecting iron-rich silicates in Earth's mantle. the rotation of the planet on its axis.The flow of iron alloy in Earth's molten outer core makes it an electromagnet. SEC: 2.3 Identify the FALSE statement Plate boundaries where subduction occurs are also called consuming boundaries. Seafloor spreading behind a volcanic island arc creates a small ocean basin called aback-arc basin or marginal sea. An accretionary prism is a wedge-shaped mass of sediment scraped off asubducting plate as it slides under the overriding plate. A spreading boundary must be in the middle of the ocean basin where it is located.The Mid-Atlantic Ridge is in the middle of its ocean, but this is not true for mid-ocean ridges inthe Pacific and Indian Oceans. SEC: 2.7, 2.8 Identify the FALSE statement. Positive magnetic anomalies occur over areas of seafloor when the poles of Earth'smagnetic field and the paleopoles preserved in the seafloor basalt agree; negativeanomalies occur when they are opposite each other. All polarity chrons are the same length of time; they differ only in the magneticstrengths they represent. The series of rock stripes parallel to and bilaterally symmetrical across the mid-ocean ridge record the sequence of Earth's magnetic reversals over time. The width of each rock stripe is a measure of how long the polar direction remainedconstant.Time intervals between reversals differ, so the lengths of polarity chrons also differ. Polaritychrons have nothing to do with magnetic strength. SEC: 2.5 Identify the FALSE statement. Plates shift the continents around as they move, so Earth's surface is constantlychanging. Plates may consist of all ocean floor or both ocean floor and continental crust. There are 12 major plates, and several microplates. The contacts between plates are called passive margins.The contact between lithospheric plates is called a plate boundary. Passive margins do not occurat plate boundaries. SEC: 2.6 Identify the FALSE statement. As the seafloor spreads, the asthenosphere rises, melts to become magma, and fillsthe space between plates. Some magma generated during seafloor spreading spills out to produce a new layerof seafloor called gabbro. Some magma generated during seafloor spreading erupts from submarinevolcanoes. Observers in research submersibles have seen submarine volcanoes.Gabbro does form along the sides of magma chambers in the crust below the ridge axis, but themagma that rises to become seafloor cools to form basalt. SEC: 2.7 Identify the FALSE statement. A subducting (or down going) plate can be either continental or oceanic lithosphere. has a trench along its seaward edge. can be charted by noting its Wadati-Benioff zone. has a volcanic arc associated with it.A subducting plate is always oceanic lithosphere. SEC: 2.8 Identify the FALSE statement. According to the mantle plume model, hot-spot plumes stream upward slowly because their hot rock is less dense than the overlying rock. can occur beneath ocean plates as well as continental plates. produce volcanoes that do not always coincide with a plate boundary. are thought to originate at the crust-mantle boundary.This model proposes that plumes originate deep in the mantle, just above the core-mantleboundary. Alternative explanations of hot-spot volcanoes propose plumes at shallow depth or noplumes at all. SEC: 2.10 Identify the FALSE statement. Oceanic lithosphere gets older and thicker as it gets farther from the ridge axis. gets cooler as it gets farther from the ridge axis. attains its maximum thickness when it is about 800 million years old. effectively does not exist beneath the mid-ocean ridge axis.Oceanic lithosphere attains its maximum thickness when it is about 80 million years old. Even ifyou did not remember the exact age, you could identify the false statement if you remember thatno oceanic lithosphere is more than 200 million years old. SEC: 2.7, Figure 2.19 Identify the FALSE statement. Plate movement is influenced by mantle convection, which creates shear at the base of plates. slab pull, in which the down going oceanic plate exerts a pull on the rest of theplate. mantle plumes, which are created when hot rock rises up from the deep mantle andcreates melting at the base of the lithosphere. ridge push, in which the elevated rocks at the ridge axis push on rocks farther fromthe ridge.Mantle plumes are the possible cause of hot spots, but they do not affect plate movement in ameaningful way. SEC: 2.12 Identify the FALSE statement. The rate of plate motion can be determined to within millimeters by using the global positioning system(GPS). can be expressed as relative plate velocity, which describes movement of one platein relation to another plate. can range from 100 to 150 cm per year. can be expressed as absolute plate velocity, which describes movement of a singleplate relative to a fixed point.Plate motion ranges from 1 to 15 cm per year. SEC: 2.12, Figure 2.32. Identify the TRUE statement associated with this diagram.The apparent polar-wander path of Africa is the same as that of Europe. Apparent polar-wander paths prove that