2-1-18 Types of Plate Boundaries

Do Now: Take out your homework, read the following, and answer the questions below in your science notebook Mount Everest rises over 7,900 m (26,000 ft) above sea level. That’s almost 5.5 miles. When Sir Edmund Hillary climbed Everest in 1953, scientists were still developing the theory that explains how mountains form. 1. Are mountains spread randomly across Earth’s surface, or do they form patterns? 2. Have mountains always existed and will they always remain? Do you think new mountains are being formed right now? 3. Why do you think scientists once struggled to explain how mountains form?

Do Now Are mountains spread randomly across Earth’s surface, or do they form patterns? Mountains are not spread randomly but are grouped together in a pattern of mountain chains. 2. Have mountains always existed and will they always remain? Do you think new mountains are being formed right now? Mountains have constantly been built up and worn down, and both processes continue today. Forces from Earth’s interior and moving tectonic plates help to build up mountains. Forces of erosion and weathering wear them down. 3. Why do you think scientists once struggled to explain how mountains form? Most changes to mountains take place much too slowly to be observed in a human lifetime. It takes millions of years for a mountain to form.

What is due tomorrow? Science Fair Lab Report! Make sure you check the class website, www.scascience7.weebly.com for the grading rubric to be sure you include all the details required.

Homework Review: Ch. 4, Lesson 3 Plate Tectonics Describe where the lithosphere is thick and where it is thin on Earth. The lithosphere is thin beneath mid-ocean ridges and thick below continents.

Homework Review: Ch. 4, Lesson 3 Plate Tectonics 2. How does the asthenosphere allow tectonic plates to move? Tectonic plates are large pieces of lithosphere. The asthenosphere is flexible like a plastic material. This enables Earth’s tectonic plates to move because the hotter, plastic mantle beneath them can flow. The interactions between these layers helps explain plate tectonics.

Homework Review: Ch. 4, Lesson 3 Plate Tectonics 3. Define divergent, transform, and convergent plate boundaries Divergent plate boundaries occur where two plates separate. Transform plate boundaries occur where two plates slide by each other. Convergent plate boundaries occur where two plates collide.

Homework Review: Ch. 4, Lesson 3 Plate Tectonics 4. Describe the three forces that cause plate motion. Convection currents in the mantle produce a force that causes motion called basal drag. Ridge push is the force of plates moving away from mid-ocean ridges. Slab pull is the force that pulls on a plate as one edge of the plate sinks into the mantle.

Plate Boundaries EQ: What are the three types of plate boundaries?

Plate Boundaries A divergent plate boundary, the boundary between two plates that move away from each other, forms where two plates separate. Limite divergente de placas: limite entre dos placas que se alejan una de la otra When the seafloor spreads at a mid-ocean ridge, lava erupts, cools, and forms new oceanic crust. Divergent plate boundaries can also exist in the middle of a continent, where they pull continents apart and form rift valleys. Example shown: Quilotoa, Ecuador

Plate Boundaries transform plate boundary: the boundary between two plates that slide past each other. Limite de placas transcurrente: limite entre dos placas que se deslizan una con respecto a la otra. As they move past one another, the plates can get stuck and stop moving. Stress builds up where the plates are stuck until they eventually break and suddenly move apart, resulting in a rapid release of energy as earthquakes. Example shown: San Andreas Fault in California

Plate Boundaries Convergent plate boundary: the boundary between two plates that move toward each other. Limite convergente de placas: limite entre dos placas que se acercan una hacia la otra.

Plate Boundaries The denser plate sinks below the more buoyant plate in a process called subduction: the process that occurs when one tectonic plate moves under another tectonic plate. Subduccion: proceso que ocurre cuando una placa tectonica se mueve debajo de otra placa tectonica. The area where a denser plate descends into Earth along a convergent plate boundary is called a subduction zone. This occurs when an oceanic and a continental plate collide.

Plate Boundaries When an oceanic plate and a continental plate collide, the denser oceanic plate subducts under the edge of the continent, creating a deep ocean trench and a line of volcanoes above the subducting plate on the edge of the continent.

Plate Boundaries When two continental plates collide, neither plate is subducted, and mountains form from uplifted rock. Example: Himalayan mountains

Rally Robin: In groups of 3, each person will pretend to be a plate boundary. Take turns sharing details about “yourself” until you are told to stop. What are the three types of plate boundaries? Convergent, transform, and divergent

Plate Tectonics BrainPop video https://www.youtube.com/watch?v=RA2-Vc4PIOY