constructive & destructive forces. eq: what is the difference between a constructive force and a...
TRANSCRIPT
• Constructive Forces- Natural forces that build or construct landforms and cause changes in the Earth’s surface.
• Examples:– Volcanoes
– Deposition
– Earthquakes
Constructive ForcesConstructive Forces
• Constructive forces affect the earth's surface by building it up to form new landforms like mountains and islands.
• Examples of these type of forces are:• Deposition is the dropping off of bits of eroded
rock. This process helps to build up Earth’s surface by filling in depressions, or basins.
• Earthquakes• Volcanoes
• Destructive Forces – Natural forces that destroy landforms and causes damaging changes in the Earth’s surface. - Earthquakes– Weathering/Erosion
– Volcanoes
Earthquakes:
• Shaking that results from the movement of rock (tectonic plates) beneath Earth’s surface
• Destructive force or Constructive force
• Most occur because of moving crust
Earthquakes causes vibration across the ground, sending shock waves that crumble buildings.http://jclahr.com/alaska/aeic/taurho/eqeffects/eqtsun.mov
Stress:
• Force that acts on rock to change its shape and volume
• Energy is stored in the rock until it breaks or changes shape
3 Types of Stress:
1. Shearing – Pushes rock in opposite directions
past each other
- Transform boundaries
3 Types of Stress:
2. Tension – Stretches rock so that it becomes
thinner in the middle
- Diverging boundaries
Faults:
• Break in Earth’s crust where slabs of crust slip past each other
• When stress builds up, the rock breaks along a fault
• Usually occur along plate boundaries
3 Main Types of Faults:
1. Strike-Slip – Rocks on each side slide past each other with little (or no) up & down motion
- Transform boundaries
- Caused by Shearing
- San Andreas (California)
Measuring Quakes:
• Seismograph –
• instrument used to measure the vibrations and seismic waves of earthquakes.
Rating Scales used for Quakes:
2. Richter – Rate quakes according to the size of the seismic waves
- low ---> high (1-9)
-each # is 10x stronger
- humans cannot feel a quake below 2
- 6 or more = major quake
- Measures magnitude
Misc. Info:
• Tsunami • – a series of seismic sea
waves- result from underwater
earthquakes, landslides, or volcanic eruptions
Volcanoes:• Destructive AND Constructive• Weak spot in the crust where molten
material from the mantle comes to the surface
• Magma – Hot molten rock located Below ground.
• Lava – magma that reaches the surface.
Weathering:
• Process that breaks down rock & other substances at the Earth’s surface- very slow process
• Temperature, Water, & gases in the atmosphere all contribute to weathering
Mechanical Weathering:
• Process by which rock is physically broken into smaller pieces
• Small pieces have same material as the original rock
• Very slow occurrence
• The most common type of mechanical weathering is the constant freezing, and thawing of water. In liquid form, water is able to penetrate the many holes and joints within a rock. As the temperature drops water freezes and expands, becoming about 10% larger than it was in liquid form. The result is that the holes and cracks in rocks are pushed outward. Even the strongest rocks are no match for this force.
Mechanical Weathering:• Caused by…(Agents)
– Freezing and Thawing– Release of Pressure– Growth of Plants
– Abrasion – Grinding away of rock by other rock particles that are
carried by water, ice, wind, or gravity
Chemical Weathering:
• Breaks down rock through chemical changes- Chemical properties are actually changed.
• Rock particles have different mineral make-up than original rock
Chemical Weathering:
• Caused by…(Agents)– H2O(Water) MOST important
– Oxygen (O2)
– Carbon Dioxide (CO2)
– Living organisms
– Acid Rain very rapid
Stalactites
Stalagmites
Stalactites & Stalagmites created by acid rain falling into these limestone caverns.
Agent Type DescriptionMechanical Rock particles wear away rock
Chemical Forms from coal, oil, and gas burning
Freezing/Thawing Breaks rock by ice wedging
Carbon Dioxide Forms carbonic acid in water
Chemical Weathers marble and limestone
Mechanical Burrowing in the ground breaks rock
Plant growth Roots pry apart cracks in rock
Living Organisms Produce weak acid that weathers rock
Oxygen Causes rust on some rock
Mechanical Sun or forest fire causes rock to crack
Erosion:• Process by which natural forces
move weathered rock & soil from one place to another (by wind, water, ice, & gravity)
• Sediment
•Material moved by weathering and erosion
Mass Movement:
• Deposition
• Caused by gravity
• Occurs where bits of rock are dropped off (deposited) because of erosion
• On land sediment can be moved down hill by:– Landslide– Mudslide