Processes Shaping the Earth (S.T.E.W.) Take a guess. What are the processes that could be currently shaping the earth RIGHT NOW?? Try to complete the acronym above for these processes.

Four Spheres of the Earth One of the ways geographers describe the earth is by spheres Physical processes that take place in the spheres create, maintain, and/or modify the features and environments of the earth.

S.T.E.W.– Soil Building Bits of rock, mixed with decaying plants and animals. The type and quality of soil determines what can grow in a particular place Alluvial plain – soil is rebuilt in a regular cycle by flood waters leaving behind sediment

S.T.E.W.– Tectonic Forces What is common where these two plates meet? The push/pull of the major plates of the earth. What is common where these two plates meet? Why?

Three types of tectonic plate boundaries Divergent – plates move apart from one another Convergent – plates move together Transform – plates slide across each other Firstly, there are three types of plate boundary, each related to the movement seen along the boundary. Divergent boundaries are where plates move away from each other Convergent boundaries are where the plates move towards each other Transform boundaries are where the plates slide past each other. Presenter: See diagrams for each - it is important to remember the names of the boundary types and the motion involved. Useful Prefixes! Di – two; apart Con – with; together Trans - Across

Divergent Boundaries Spreading ridges: 1) Plates move apart 2) New material is erupted to fill the gap Contributes to creation of volcanoes and islands In plate tectonics, a divergent boundary is a linear feature that exists between two tectonic plates that are moving away from each other. These areas can form in the middle of continents or on the ocean floor. As the plates pull apart, hot molten material can rise up this newly formed pathway to the surface - causing volcanic activity. Presenter: Reiterate the process by going through the diagram, including the presence of mantle convection cells causing the plates to break apart and also as a source for new molten material. Where a divergent boundary forms on a continent it is called a RIFT or CONTINENTAL RIFT, e.g. African Rift Valley. Where a divergent boundary forms under the ocean it is called an OCEAN RIDGE.

Convergent or Subduction Boundaries Plates collide into each other creating high mountains Himalayas Andes

Transform Boundaries Where plates slide past each other Above: View of the San Andreas transform fault Major source of earthquakes Tibetan video? The third type of boundary are transform boundaries, along which plates slide past each other. The San Andreas fault, adjacent to which the US city of San Francisco is built is an example of a transform boundary between the Pacific plate and the North American plate. Epicenter – origin of an earthquake

S.T.E.W. – Erosion Material is moved by the action of WIND, WATER, or ICE WATER: Motion of water picks up soil – river Abrasive action of waves – grind down rock, carries soil away. WIND: wind carries soil, stronger wind heavier particles can be carried. ICE/GLACIER: As ice moves it carved and grinds the rocks, also transporting soil. (Fjords & Valleys) https://youtu.be/J-ULcVdeqg Bill nye

S.T.E.W. - Erosion/Weathering Erosion - the process by which broken down rock is moved

Main Physical Processes – Erosion and Weathering Weathering – the gradual wearing down of rocks by wind, water, or ice. Can be mechanical or chemical

Chemical v Mechanical Weathering Chemical changes composition by chemical decay Mechanical/Physical changes by physical force

Chemical Weathering Acid Rain and Statues Watch Carefully. If rain can do this to a statue over a relatively short period of time, then how else might acid rain affect the earth?

Main Physical Processes – WEATHER or Climate Meteorological conditions such as temperature, precipitation, wind, etc. (often combine with soil building and erosion)

Erosion ( and Weathering) Weather (or Climate) Review What does S.T.E.W. stand for? Soil Building Tectonic Forces Erosion ( and Weathering) Weather (or Climate)