Presentation on theme: "Our Dynamic Earth. Earth as a System The Earth is an integrated system that consists of rock, air, water, and living things that all interact with each."— Presentation transcript:
Our Dynamic Earth
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)
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. A seismic wave is altered by the nature of the material through which it travels.
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.
Processes and Forces that Affect the Lithosphere Rock Cycle Weathering Erosion Soil Formation Plate Tectonics Earthquakes Volcanoes Humans
Rockin’ the Rock Cycle
Rock Cycle Rocks are continually changed by many processes, such as weathering, erosion, compaction, cementation, melting, and cooling Rocks can change to and from the three types through the rock cycle.
What is a Rock? Naturally-occurring mixtures of minerals, mineraloids, glass or organic matter. Rocks are divided into 3 groups based on how they were formed: IGNEOUS SEDIMENTARY METAMORPHIC
Igneous Rock Igneous rock is made when magma cools and crystallizes. (Igneous means “from fire or heat”) Type of Igneous Rock Where does it Form? How does it Cool? What Size Grains does it have? Example Intrusive Inside Earth SlowlyLarge (Course) Granite Extrusive Outside Earth QuicklySmall (Fine) or Glassy (Very Fine) Basalt Obsidian
Examples of Igneous Rock Granite: Large/Course Grains Basalt: Small/Fine Grains Obsidian: Glassy/Very Fine Grains
What happens to the Igneous Rock? 1. It can be weathered and eroded and turned into small pieces, called sediment, which can then be turned into a sedimentary rock. 2. It can be put under high heat or pressure and form a metamorphic rock. 3.Could melt and become magma again
Sedimentary Rock 1. Rock is weathered and forms sediments – Sediments: smaller pieces of rock Examples: Gravel, Sand, Mud, Soil
Sedimentary Rock 2. Erosion – The process by which weathered rock and soil particles are moved from place to place by wind, water, gravity, glaciers, etc. 3. Deposition – The process by which weathered sediments are laid down in a new location creating new landforms through “bedding”.
3. Deposition – Types of Bedding 1.Bedding – oldest sediments on the bottom, youngest sediments on top 2. Graded Bedding – biggest sediments on bottom, smallest on top (happens in water) 3. Cross Bedding – sediments are laid at an angle (ex: sand dunes)
Sedimentary Rock 4. Lithification - Sediments must be buried, compacted, cemented together to make a sedimentary rock. Examples of Sedimentary Rock: CoalSandstoneShale
What happens to Sedimentary Rock? 1. Could weather and erode to become sediments which cement and compact to form sedimentary rock 2. It can be put under high heat or pressure and form a metamorphic rock. 3.Could melt to form magma which cools and hardens to form igneous rocks.
Metamorphic Rock Limestone (Sedimentary) Marble Shale (Sedimentary) Slate Granite (Igneous) Gneiss Formed from existing rocks. Are created by intense heat or intense pressure. Can be foliated = looks like it has layers (made from pressure) Can be non- foliated = does not look like it has layers (made from heat)
What happens to Metamorphic Rock? 1.Could weather and erode to become sediments that cement and compact to form sedimentary rocks 2. Could melt to form magma which cools and hardens to form igneous rocks
How are rocks redistributed? The core, mantle, & crust are one giant rock recycling machine changing the lithosphere.
Weathering is the breaking down of rocks and other materials on the earth ’ s surface
Physical Weathering Breaks rock into smaller pieces without changing the overall composition. Examples- Biological Activity (tree roots and animals burrowing), Frost Wedging (water freezing inside cracks of rocks causing them to expand and break), Gravity
Chemical Weathering Chemical reactions that change the overall composition of the rock. Examples- Water (most important agent), Acid Rain on gravestones (dissolves minerals), Oxidation
Factors that determine the rate of weathering: oComposition Granite more resistant than marble. oPhysical conditions of rock Cracks, holes, crevices – easier weathering Solid, unbroken – more weather resistant oTopography: the position of the rock oAir pollution oExposure time oSurface area exposed oClimate oCold Climates – mechanical weathering breaks down rocks rapidly Warm, wet climates – chemical weathering breaks down rocks rapidly Mechanical and chemical weathering work together
5 Agents of Erosion Gravity Glaciers Wind Water Ocean Waves
Followed by… Some living organisms such as bacteria, fungi and insects. They die, decay and add nutrients to the soil.
So Basically… Soil is a layer at the surface of the earth composed of a mixture of weathered rock, organic matter, mineral fragments, water, and air which is capable of supporting the growth of plants impacting the lithosphere.
What observations can you make about the shape of the continents?
What’s interesting? Just 200 million years ago, this is what the world looked like:
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
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.
Plate Boundaries Divergent Boundary:
Plate Boundaries Divergent Boundary: Plates are moving away from each other Midocean ridges are created and new ocean floor plates are created
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
Plate Boundaries Convergent Boundary Convergent Boundary: plates are moving toward each other and are colliding (3 types)
Convergent Boundaries Create subduction zones, trenches Create near coast volcanoes Island arcs are created Mountain ranges are created – (example: Himalayan Mountains)
Plate Boundaries Transform Fault Boundary Plates are neither moving toward nor away from each other, they are moving past one another.
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)
San Andreas Fault
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?
Tensional Force: stretching or pulling Creates a normal fault What types of forces are created?
Compressional Force: force pushing something together Creates a reverse fault What types of forces are created?
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?
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.
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
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
How do we Measure Earthquakes? Earthquake waves are recorded by a seismograph and the recording of waves on paper is called seismogram
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
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.
Where do Earthquakes Occur?
Landslides Avalanches Earthquake Dangers
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.
Volcanoes: The Ring of Fire
The Birth of a volcano
What comes out of volcanoes ? Lava Tephra Gases
Tephra Basically, rock fragments Also known as pyroclastic rock fragments. There are many different possible sizes, from very small (volcanic ash or dust to much larger rocks (called volcanic bombs)
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
Trapped gases under high pressure will violently explode Has granitic magma The high water content of the magma produces more water vapor which when mixed in granitic magma produces explosive eruptions Explosive Eruptions
The eruption of Mt. St. Helens in 1980
Low Pressure gas Has basaltic magma (is more fluid and will flow instead of explode) …and has low water content Examples: Hawaii Quiet Eruptions
A typical Hawaiian Eruption
Types of volcanoes
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 (lahar) 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.
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.
Human Impact on the Lithosphere
Urbanization Destroying natural areas can reduce the beauty of an area and have a potential economic impact. Rapid development can result in very high levels of erosion and sedimentation in river channels. Pollution of soils is possible by leaking gas tanks and other chemicals.
Agriculture Agriculture takes space. Use of chemical pesticides, insecticides and fertilizers can contaminate soil and affect soil fertility. – Organic fertilizers are better. Planting the same crop over and over can strip vital minerals out of the soil. – Crop rotation can help.
Deforestation Cutting down all the trees in an area loosens the soil and makes it very easy for extreme erosion to occur. One solution is replanting and a system of harvesting that thins out the area.
Overgrazing Overgrazing is the removal of excessive amounts of plant growth by animals in one area. This accelerates erosion and strips away topsoil, resulting in no plants able to grow. It is best to rotate animals among pastures.
Mining Strip Mining Underground mining requires digging out large areas, increasing the risk for sinkholes and cave ins. Strip mining destroys the environment. Mine operators must reclaim the land after mining is finished (put the land back together and restore it to its original condition).
Harvesting Peat Peat is an accumulation of partially decayed vegetation. Eventually, peat can turn into coal and be burned for fuel. Advantages – low sulphur content – minimal mercury content – low ash content energy – values equivalent to coal, less expensive than oil and natural gas and competitive with other biofuels – minor engineering retrofit needed when substituted for, or blended with, coal Since peat forms nearer to the surface, it requires less digging.
Drilling for Oil and Natural Gas Oil and Natural Gas are nonrenewable resources. Drilling can cause the lithosphere to be disturbed and can cause earthquakes. Soil and groundwater can also be contaminated. – Fracking is a hot political topic.
Human Activity and the Coast As more and more people retire, there is more development on our coast. Removal of vegetation at the coast can cause serious erosion. Man made erosion control, like sandbags, can make erosion worse downshore. Erosion causes houses to be condemned and potentially fall into the ocean.