2. Our Dynamic Earth

3. Earth as a System The Earth is an integrated system that consists of rock, air, water, and living things that all interact with each other. Scientists divided this system into four parts: The Geosphere (rock) The Atmosphere (air) The Hydrosphere (water) The Biosphere (living things)

4. Earth as a System

5. Earth’s Interior Scientists use seismic waves to learn about Earth’s interior. Seismic waves are the same waves that travel through Earth’s interior during and earthquake.

6. Seismic Waves A seismic wave is altered by the nature of the material through which it travels. Seismologists measure changes in the speed and direction of seismic waves that penetrate the interior of the planet. With this technique seismologists have learned that the Earth is made up of different layers and have inferred what substances make up each layer.

7. Layers of the Earth Scientists divide the Earth into three layers: – The crust – The mantle – The core These layers are made up of progressively denser material toward the center of the Earth.

8. Layers of the Earth  The Earth can be divided into five layers based on the physical properties of each layer.  lithosphere - solid, outer layer of the Earth that consists of the crust upper part of the mantle; divided into huge pieces called tectonic plates.  asthenosphere - solid, plastic layer of the mantle beneath the lithosphere; made of mantle rock that flows slowly, which allows tectonic plates to move on top of it.

11. What observations can you make about the shape of the continents?

12. What’s interesting? Just 200 million years ago, this is what the world looked like:

13. Plate Tectonics  Tectonic plates - blocks of lithosphere that consist of the crust and the rigid, outermost part of the mantle and glide across the underlying asthenosphere.  The continents are located on tectonic plates and move around with them.  The major tectonic plates include the Pacific, North America, South America, Africa, Eurasian, and Antarctic plates

14. Plate Boundaries Much of the geological activity at the surface of the Earth takes place at the boundaries between tectonic plates. Tectonic plates may separate, collide, or slip past one another.

15. Plate Boundaries Divergent Boundary:

16. Plate Boundaries Divergent Boundary:  Plates are moving away from each other  Midocean ridges are created and new ocean floor plates are created

17. Leif the Lucky Bridge Bridge between continents in Reykjanes peninsula, southwest Iceland across the Alfagja rift valley, the boundary of the Eurasian and North American continental tectonic plates. Rift Valleys

18. Plate Boundaries Convergent Boundary Convergent Boundary:  plates are moving toward each other and are colliding (3 types)

19. Convergent Boundaries Create subduction zones, trenches Create near coast volcanoes Island arcs are created Mountain ranges Mountain ranges are created – (example: Himalayan Mountains)

20. Himalayan Mountains

21. Plate Boundaries Transform Fault Boundary  Plates are neither moving toward nor away from each other, they are moving past one another.

22. Transform Fault Boundary  The plates may move in opposite directions or in the same directions but at different rates and frequent earthquakes are created (example: San Andreas Fault)

23. San Andreas Fault

24. oNo oPlates are destroyed as fast as they are created (2 ways) oPlates may be subducted and melted or may push be pushed upward to form mountains So is the Earth getting bigger?

25. Tensional Force: stretching or pulling Creates a normal fault What types of forces are created?

28. Compressional Force: force pushing something together Creates a reverse fault What types of forces are created?

30. Shear or Transversal Force: a system of forces that operates against a body from different sides Creates a strike-slip fault What types of forces are created?

33. Convection currents within the mantle  The up-welling leg of the current creates a divergent boundary which produces midocean ridges What causes this?

35.  The down-welling leg of the current creates one type of convergent boundary that results in trenches and a subduction zone

37. Earthquakes A fault is a break in the Earth’s crust along which blocks of the crust slide relative to one another. When rocks that are under stress suddenly break along a fault, a series of ground vibrations, known as earthquakes, is set off. Earthquakes are occurring all the time. Many are so small that we cannot feel them, but some are enormous movements of the Earth’s crust that cause widespread damage.

38. Earthquakes  The actual place underground where the earthquake starts and rocks break producing vibrations is called the focus.  The place on the surface directly above the focus is called the epicenter

39. Originate at the focus and travel outward in all directions – Three Types: P wave, S wave, surface waves Foreshocks: small earthquakes that come before a major earthquake Aftershocks: Are adjustments in the crust after in earthquake. – Smaller than main earthquake, but can cause as much or more damage. They can continue for weeks to months. Seismic Waves

40. How do we Measure Earthquakes? Earthquake waves are recorded by a seismograph and the recording of waves on paper is called seismogram

41. Locating the epicenter 1.Lag time between the arrival of the P wave and the S wave to the seismograph station is converted to a distance 2.A circle with a radius that equals the distance is drawn around the station. 3.Three stations can narrow down the location to where the circles intersect Locating the focus: the lag-time of the surface wave will determine the depth of the focus Measuring Earthquakes

45. Earthquakes The measure of the energy released by an earthquake is called magnitude. The smallest magnitude that can be felt is 2.0, and the largest magnitude ever recorded is 9.5. Magnitudes greater than 7.0 cause widespread damage. Each increase of magnitude by one whole number indicates the release of 31.7 times more energy than the whole number below it.

46. Where do Earthquakes Occur? The majority of earthquakes take place at or near tectonic plate boundaries because of the enormous stresses that are generated when tectonic plates separate, collide or slip past each other. Over the past 15 million to 20 million years, large numbers of earthquakes have occurred along the San Andreas fault in California, where parts of the North America plate and the Pacific plate are slipping past one another.

47. Where do Earthquakes Occur?

48. Earthquake Dangers oMost injuries and deaths are caused by falling objects and most property damage results from fires that start Tsunami: seismic sea wave sometimes generated when an earthquake originates on the ocean floor Tsunami

50. Landslides Earthquake Dangers

52. Volcanoes  A volcano is a mountain built from magma, or melted rock, that rises from the Earth’s interior to the surface, and can occur on land or in the sea.  Volcanoes are often located near tectonic plate boundaries where plates are either colliding or separating from one another.  The majority of the world’s active volcanoes on land are located along tectonic plate boundaries that surround the Pacific Ocean.

53. Volcanoes: The Ring of Fire

54. The Birth of a volcano

55. What comes out of volcanoes ? Lava Tephra Gases

56. Tephra rock  Basically, rock fragments pyroclastic Also known as pyroclastic rock fragments. ash dust bombs There are many different possible sizes, from very small (volcanic ash or dust to much larger rocks (called volcanic bombs)

57. GASES water vapor, carbon dioxide, nitrogen, sulfur dioxide, hydrogen sulfide, chlorine

58. Two factors determine the type of eruption :  Amount of water vapor & other gases in the magma  The chemical composition of the magma Types of Volcanic Eruptions

59.  Trapped gases under high pressure will violently explode when the magma reaches the lower pressure of the surface. Explosive Eruptions

60.  Has granitic magma is very thick and plugs the vent causing the pressure to build until it blows violently out the vent Explosive Eruptions Mt. St. Helens

61.  The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions Explosive Eruptions Mont serrat

62. The eruption of Mt. St. Helens in 1980

63.  Low pressure gas Quiet Eruptions

64.  Has basaltic magma (is more fluid and will flow instead of explode) Quiet Eruptions

65.  …and has low water content  Examples: Hawaii Quiet Eruptions

66. A typical Hawaiian Eruption

67. Types of volcanoes

68. Local Effect of Volcanic Eruptions  Clouds of host ash, dust, and gases can flow down the slope of a volcano at speeds of up to 200 km/hr and sear everything in their path.  During and eruption, volcanic ash can mix with water and produce mudflow that runs downhill.  In addition, ash that falls to the ground can cause buildings to collapse under its weight, bury crops, damage the engines of vehicles, and cause breathing difficulties.

69. Global Effect of Volcanic Eruptions Major volcanic eruptions can change Earth’s climate for several years. In large eruptions, clouds of volcanic ash and sulfur rich gases may reach the upper atmosphere, and spread across the planet reducing the amount of sunlight that reaches the Earth’s surface. The reduction in sunlight can cause a drop in the average global surface temperature.