NATIONAL MINING UNIVERSITY MINING FACULTY Underground Mining Department

NATIONAL MINING UNIVERSITY MINING FACULTY Underground Mining Department TECTONIC PROCESSES Postgraduate Malashkevych D. S. . NMU

Plate tectonic theory Plate tectonics is an important theory developed in the 1960 s to explain how the continents move across the Earth's surface. Early 20 th century geologist Alfred Wegener developed theory of continental drift. He realized that the puzzle-like fit of many the continents was more than a coincidence, but he couldn't correctly explain what powered their movement. Alfred Wegener (1880 -1930) NMU

What is plate tectonics? Plate tectonics is theory that Earth's outer shell is divided into dozen large plates and several smaller plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. These plates are constantly moving. NMU

Movement Plate tectonics are the mechanics of the movement of the plates. According to the US Geological Survey, The fastest plate races along at 15 centimeters (6 inches) per year while the slowest plates crawl at less than 2. 5 centimeters (1 inch) per year. To humans this is incredibly slow, but in geological time it is movement on a massive scale. In one million years the fastest plates will have moved 6 million inches or 500, 000 feet. This means that this plate could move a little over 94 miles (150 km). This would move Los Angeles north to where Santa Barbara is located. So in about 30 million years Hawaii will be part of Alaska. NMU

How do plates moves? The movement of the plates is a simple concept. Under the crust of the Earth is the mantle. It is a hot area with semi-solid liquid. The magma closest to the Earth's core is super-hot and rises the currents of heat towards the upper levels of the mantle. As it rises, the liquid cools and becomes more solid. It also becomes heavier. These semi-solids sink and reheat on the way down towards the core. Imagine giant circles of heat driven movement. This may go on below the surface, but it affects the surface. The tectonic plates of the Earth are riding on these convection currents. These convection currents shift the plates. NMU

Movement The movement of the plates creates three types of tectonic boundaries: convergent, where plates move into one another; divergent, where plates move apart; and transform, where plates move sideways in relation to each other. NMU

Convergent boundaries The destruction or recycling of the Earth’s crust takes place at convergent boundaries. Convergent boundaries are the zones where two tectonic plates moving towards each other. The type of collision depends on the types of plates. These can be categorized as: Oceanic – Continental Plate Convergence Oceanic – Oceanic Plate Convergence Continental – Continental Plate Convergence NMU

Oceanic-continental plate convergence When an oceanic plate collides with a continental plate the crust forming the oceanic plate gets bent and pulled under the continental crust. This process is called subduction and the zone at which this occurs at the plate boundaries is called the subduction zone. At the subduction zone where the oceanic crust sinks beneath the continental crust a deep oceanic trench or valley is created. These can be many of thousands of kilometres long and 8 to 10 kilometres deep making them the deepest part of the ocean floor. Mountains are formed as the overriding continental plate gets lifted up over the oceanic plate NMU

Oceanic-oceanic plate convergence This is similar to oceanic-continental convergence in that one of the plates is subducted under the other during the collision. Oceanic and oceanic plate convergence result in the formation of volcano chains. The crust that is pulled under or subducted melts to form magma. This magma rises to the top of the overriding oceanic plates and erupts on the ocean floor. Over millions of years, the lava and debris from the volcanic eruptions pile up on the ocean floor until the volcano rises above sea level to form a volcanic island. These types of islands are usually formed as chains called island arcs, which run parallel to the trench at the subduction zone. NMU

Continental-continental plate convergence When two continental plates collide they resist downwards motion or subduction because the continental rocks that make them up are similar density. Instead, the crust tends to buckle and gets pushed upwards and sideways. Thus, when two continental plates collide mountains are formed. Over millions of years the continuous collisions between the two plates has resulted in the formation of the Himalayan mountain range and the Tibetan Plateau. The Himalayas are the highest continental mountains in the world holding many peaks at 8000 meters above sea-level, the highest being Mount Everest at 8848 meters. Since the Indian Plate is continuing in its northward movement into the Eurasian plate the Himalayas continue to grow at a rate of approximately 5 mm to 20 mm a year. NMU

Divergent boundaries are the zones where two tectonic plates are moving away from one another. Divergent boundaries are constructive boundaries because new crust is generated by magma pushing up from the mantle as the plates pull away from each other. NMU

Transform boundaries At a transform boundary plates slide or, more accurately, grind past each other horizontally. Transform boundaries also occur at mid-ocean ridges, as these are separated into segments, cut crossways by cracks where the rocks on either side move past, rather than away, from each other NMU

1. What is plate tectonics? 2. Please tell us the definition of tectonic plate 3. What is the value of the slowest and the fastest plates crawl? 4. How many types of tectonic boundaries do you know? 5. What is the highest point of the world? NMU

Thank you NMU