.. ent kinds of active plate boundaries. An example of the most well known and studied fault is the San Andreas Fault located of the coast of California. 11. The origin of volcanoes: Hot spots, can be found on plate boundaries or inside the plates.
The hot spot is a place deep inside the Earth that begins to form molten lava from extreme heat conditions. It will quickly rise up, pushing and melting its way to the surface resulting in a volcano. Because of the constant moving of the plates, the volcano will be carried away from the hot spot and become dormant. This process will repeat itself, forming a never-ending row of volcanoes. 12.
The crust, being the absolute outer layer of the Earth is made up of the every day surface rocks like granite, basalt, limestones and so on. The mantle is made up of dark, dense rocky materials that are denser then the above-mentioned crust. The mantle will take up the largest part of the Earth’s interior, lying in-between the crust and the core. The lithosphere lies in the upper 100 kilometers of the Earth’s body. The lithosphere takes a much more rigid abuse because of the surrounding temperature being much under the melting point.
The lithosphere zone is also responsible for creating the rigid plates called lithospheric plates. Lying directly under the lithosphere zone is the asthenosphere. Located in the low velocity zone, it’s constantly exposed to extreme borderline melting temperatures. This results in making this zone very soft and equally weak. 13.
Scientists will use paleomagnetism to study the Earth’s magnetic field found inside rocks. Acting like a compass, the northern magnetic field will cause cooling lava to freeze in the direction of the magnetic field. The Earth’s magnetic field has been known to switch directions (magnetic polarity reversals). When this occurs it will only take a few thousand years to flip to the opposite position. Magnetic reversals are a great tool for measuring the movements of the oceanic plates.
Sea floor spreading will be altered dramatically, depending on the current direction of the magnetic field. When the magnetic field is in its normal direction, the oceanic floor spreading will be magnetized normally. But if the magnetic field is reversed, newly formed oceanic floor will become reversely magnetized. If magnetic fields in the sea floor match, it will create a smooth and flat surface. So combining paleomagnetism and sea floor spreading allows scientists to track the exact movement of the plates on both sides of the ridge. 14. In the last 250 million years there have been significant movement and change in the Earth’s major crustal plates, resulting in continents moving.
Bringing us to the Triassic period, Asia had been mostly put together and a number of continental collisions caused mountains to form, creating the now Appalachians. During the middle of the Jurassic period, Pangea (all land) had been formed. Pangea was one giant continent surrounded by a world of ocean. During the ladder half of Jurassic, Pangea began to move, break apart and rotate clockwise, destroying land so that India and Asia were now separated. During these changes the North Atlantic began to open up and the ocean floor we see today began to show itself. Subduction of the ocean floor under the west coasts of North and South America created what we know now as the Andes and the Sierra desert of Nevada and California.
Coming to 60 million years ago, Australia had split from Antarctica going south while Antarctica traveled north. To this day Africa still continues to move north, while Italy breaks through Europe creating the Alps. And continental collisions by India and Asia are still occurring, forming the Himalayas higher and higher. 15. The impact and strength of an earthquake can be measured in 2 different ways. The first most well known method is the Richter scale.
The Richter method, being a 1-10 scale is based on the measurement of the ground shaking of a certain point located a distance from the actual earthquake. The Richter scale is only a rough indicator of the absolute total energy released from the earthquake. This brings us to the Modified Mercalli Intensity scale that unlike the Richter; it does not involve the expensive high-tech equipment used for the Richter method. The Mercalli method is to observe change and interview witnesses involved in the earthquake and then constructed in a special scale from I-XII, I being not felt except by very few to XII total damage and catastrophic destruction. 16. Rifts, Subductions, and Faults are types of crustal plate boundaries that react similar to earthquakes or volcanoes.
Like volcanoes, rifts are created by plates pulling away causing cracks to fill up with lava, causing new floor to reveal itself. Faults are fractures in rocks that have been displaced on both sides facing each other. The fault is also a cozy home for earthquakes. Subductions will also cause earthquakes when plates run into one another and overlap. As a result of the plates overlapping the under crust will bend under into the mantle. Unit IV 17.
In the event of an earthquake, vibrations will be produced, causing seismic waves. There are two types of waves that have the ability to travel deep within the body of Earth. First is P waves that are the fastest moving waves, resulting in the first wave to be recorded. To move as fast as they do, they must have the ability to penetrate solids, liquids and gases. S waves will travel slower in a snake-like pattern. Unlike P waves, the S wave cannot pass through liquids or gasses because of it depending on the medium’s resistance to sideways deformation. 18. Knowing these facts about seismic waves enables us to learn a great deal about the Earth’s core. Because that we know S waves are unable to penetrate liquid or the core-mantle boundary, we can assume its a liquid substance. Modern seismology can also detect how long it takes waves to travel from point a to point b along the surface.
From that information, it’s now possible to create a picture of the Earth’s interior. Noticing the velocity increase in P waves entering the inner core leads us to believe its solid. 19. The Earth’s structural blue prints simply show this: We start with the ground we live on and travel below the thin crust to rocks like granite and other well-known rock types. Then we reach the mantle containing very dense materials like olivine, garnet, proxenes, and spinel. The mantle is immense in size and takes up 83% of the Earth’s volume. As we travel halfway to the center, we run into the core.
The core consists of molten iron and sulfur which takes a white-hot form. This brings us to the free-floating huge iron ball, measuring 1,500 miles across. 20. When liquids and gasses of extreme high temperature travel to a cooler location, they will begin to transform and take the form of a solid-state. Scientists believe the convective motions of the asthenosphere inside the mantle cause the plates to shift on the Earth’s surface.
Unfortunately at present day, scientists can not be certain of the effect mantle convection have on the moving of tectonic plates. Science.