Constructive & Destructive Forces
Intro: Constructive Forces Processes that create landforms. Destructive Forces Processes that destroy landforms.
Intro: Constructive Forces Volcanoes Deposition Landslides Floods Destructive Forces _Weathering/Erosion Volcanoes Landslides Earthquakes Floods
Weathering: Process that breaks down rock & other substances at the Earth s surface Temperature, water, wind, and plants all contribute to weathering
2 Types of Weathering: 1. Physical 2. Chemical
Physical Weathering: Rock is physically broken into smaller pieces. Small pieces have same composition as the original rock. Very slow
Chemical Weathering: Breaks down rock through chemical changes Rock particles have different mineral make-up than original rock
Erosion: Process by which natural forces move weathered rock & soil from one place to another (by wind, water, waves, ice, & gravity) Sediment Material moved by weathering/erosion
Deposition: Deposition is the dropping, or depositing, of sediments by water, wind, or ice. Deposition builds up new land on Earth s surface, like a delta at the end of a river or the pile of a sand dune in the desert. Shells on the beach are deposition by ocean waves.
Creep: Very slow downhill movement of rock & soil
Earthquakes: Earth is made of layers. The crust is the thinnest layer. The crust is made up of giant slabs of rock called plates. When plates move, earthquakes may occur.
Earthquakes: Earthquakes are movements in Earth s crust that are caused by a sudden shift of Earth s plates. Destructive force Mountains and volcanoes form as plates move.
Where Earthquakes Happen: Most earthquakes occur near the edges of Earth s plates. There is an area around the Pacific Ocean where some of Earth s plates meet. It is here that most earthquakes happen.
What causes an earthquake: Plates are always moving. Sometimes, they move slowly. At other times, the motion is sudden. The energy released by the sudden motion of plates shakes the crust. It can set a large earthquake in motion.
What is a Tsunami? A tsunami is a giant ocean wave. Tsunamis are usually caused by earthquakes on the ocean floor. A few are caused by underwater landslides and volcanoes. Can move faster than 700 m/hr.
Effects of a Tsunami Tsunamis can destroy land and cause great damage if they come ashore.
Volcanoes: Destructive AND Constructive Weak spot in the crust where molten material from the mantle comes to the surface Magma Below ground, Higher temp. Lava magma that reaches the surface
What is a volcano? A volcano is a mountain that builds up around an opening in the Earth s crust. Sometimes, melted rock, gases, and pieces of rock are forced out of the volcano. This is called an eruption.
Where do volcanoes begin? When Earth s plates move, sometimes they bump into each other. As a result, one plate is pushed down deeper inside the Earth. When this happens, magma is pushed to the surface. This can cause a volcanic eruption.
Volcanoes: May not always include magma reaching the surface Hot Springs Geysers
Locations of Volcanoes: There are many volcanoes along the edge of the Pacific Plate. Ring of Fire Major belt of volcanoes that encircles most of the Pacific Ocean
Vent opening through which molten rock & gas escape Pipe long tube through which magma moves from the magma chamber to the surface Crater bowl shaped area that forms around a central vent Side Vent Magma Chamber pocket beneath a volcano where magma collects Parts of a Volcano
Effects of Volcanic Eruptions: The lava and ash can destroy forests and bury fields. Volcanic eruptions can even change Earth s weather patterns.
Volcanic Eruptions on the Ocean Floor: Volcanic eruptions, called seamounts, can also occur under the oceans. These volcanoes that are built up are called seamounts. If the seamount rises above the ocean surface it is called a volcanic island (for example Hawaii or Japan.)
Types of Volcanic Eruptions: 2. Explosive - Thick & sticky magma plugs up the pipe where pressure builds up - Breaks lava into pieces that quickly cool & harden - Ash, cinders (pebbles), & bombs hurled out - Mt. Saint Helens
Volcano All-Stars: Kilauea - Hawaii - Most active volcano in world
Volcano All-Stars: Krakatoa - Pacific Island - 1883 eruption heard 2000 miles away
Volcano All-Stars: Mt. Saint Helens - Washington state - Erupted May 18, 1980 - Leveled trees for 25 miles (Pyroclastic flow)
Volcano All-Stars: Olympus Mons - Mars - Largest Mtn./volcano in Solar System - Size of Ohio
Mass Movement: Caused by gravity Process that moves sediment downhill 4 types Landslide - Slump Mudslide - Creep
Landslide: Most destructive When rock & soil slide quickly down a steep slope
Landslide: Landslides are mass movements of land due to gravity. Landslides can cause buildings to fall, or power and gas lines to break. Landslides even occur on the continental slope in the ocean.
Mudflow: Rapid downhill movement of H 2 O, rock, and soil Often occurs after heavy rains
Slump: A mass of rock & soil suddenly slips down a slope (in a large mass/clump)
Flood: A large amount of water covers the land. It can cause rapid erosion (destructive), but also deposition (constructive).
Flood: Flood occurs when a large amount of water covers land that is usually dry. When the flood occurs, rapid erosion can take place and move soil and sediments away. When the flood recedes, new sediment is left behind and can build up rich soil deposits.