Landform Forces: Constructive vs. Destructive

1. Constructive and Destructive Landforms

2. Two Types of Forces • Destructive Forces: processes that destroy landforms. • 2 types: Slow (weathering) and Fast (Erosion) • Ex. landslides, volcanic eruptions, earthquakes, floods • Constructive forces:forces that build up an existing landform or create a new one. • Caused by: water, gravity, wind and glaciers. • Ex: deposition, landslides, volcanic eruptions, floods

3. Weathering • Weathering is the breaking down of rocks into smaller pieces. • Rain, ice, and atmospheric gases cause this.

4. Physical/Mechanical weathering • Rocks are broken into smaller pieces by physical agents. • Ice wedging. • Plant and animal actions. • Water

5. Chemical weathering • Breaking down of rocks due to the chemical change in their composition. • Air and water often cause this. • Oxidation (rust) and acid rain.

6. Erosion • The process that moves rock material at Earth’s surface and caries it away. • Movement of the rock particles.

7. Causes of erosion… • Gravity-landslides/rockslides. • Running water-rivers form canyons • Groundwater-underground water forms caves/caverns • Glaciers-rocks are carried under a glacier. • Wind-rock particles are blown • Ocean currents-sand is moved along a beach by waves.

9. Constructive Landform Processes • Processes that build up Earth’s surface and cause the land surface to rise.

10. Deposition • The process by which eroded material is dropped off or deposited in a new area. • Gravity • Water • Wind • Glaciers • Ocean currents

11. Volcanic Eruptions • Volcano: ??? • an opening in the Earth’s crust through which steam, lava and ashes erupt. • Cause both destructive and constructive changes to landforms.

12. Volcanoes can be constructive, but also destructive…

13. Folding and Faulting • Forces in Earth’s surface caused by the movement of Earth’s plates squeezes and bends the surface of Earth. • Folding occurs when the crust is bent upward or downward. • Faulting occurs when the crust is actually broken.

14. Volcanic Activity • The movement of liquid rock underground and on earth’s surface. • Magma is hot liquid rock beneath the Earth’s surface. • Magma is less dense than solid rock so it rises to the surface. • This forms a volcano.

15. When volcano’s erupt, they release hot liquid rock called lava. • Lava will harden forming new landforms.

16. Mount St. Helens Saint Helen’s Before Saint Helen’s After

17. Earthquakes • Earthquakes: the shaking of Earth’s surface caused by the release of energy along a fault. San Andreas Fault, California

18. Volcanoes & Earthquakes Tectonic Plates, Volcanoes & Earthquakes

19. Landforms from Erosion • Canyons/valleys • Flowing water removes sediment.

20. Sea cliffs • Waves erode rock making steep cliffs.

21. Sea caves, arches, and stacks.

22. Landforms from Deposition • Flood plains • Sediments deposited when rivers overflow their banks.

23. Deltas and Alluvial Fans • When a stream flows into a large body of water (lake/ocean) or onto land, it deposits sediment in a fan shape. • Delta-fan shaped pattern in a lake or ocean. • Alluvial fan-fan shaped pattern on land.

25. Water Erosion & Deposition • River Delta- Deposits of sediment at the mouth of the Mississippi River creating new land called a delta.

26. Beaches • Area of shoreline made up of sediment deposited by ocean currents and waves.

27. Landforms from Folding and Faulting • Block mountains • Large areas of Earth are forced upwards in a fault.

28. Rift valley • When two pieces of Earth’s surface are separating from each other.

30. Folded mountains • When the surface of Earth is bent upward making a mountain.

31. Landforms from Volcanic Activity • Volcanoes

32. Dome mountain • Magma forces the surface of Earth up into a dome shaped mountain.

33. Plateau

34. Primetime • What are two examples of destructive forces? • What are four examples of constructive forces? • Give an example where constructive and destructive forces work together to create a landform.