Presentation on theme: "Chapter 16 Land and Land Use Geology and Nonrenewable Mineral Resources."— Presentation transcript:
Chapter 16 Land and Land Use Geology and Nonrenewable Mineral Resources
What is geology? Geology is the science devoted to the study of dynamic processes occurring on the earth’s surface and in its interior. A geologist – a scientist that studies the processes and composition of the earth.
Continental Drift Theory In 1915, Alfred Wagner theorized that all the present day continents formed one landmass (called Pangaea) about 200 million years ago and that the landmass broke apart into smaller continents over time. Fossilized tropical plants found in Greenland’s icecaps, glacial landscapes in Africa and the continents fitting together like a puzzle- all helped him formulate his theory.
Sea Floor Spreading Theory Alternating magnetic properties of rocks found on the sea floor suggested that the ocean basins are growing and spreading apart. Magma from deep in the earth creates new ground – new crust is made. This forces other ground to sub duct somewhere else on the planet. (There is a mid-ocean ridge under the Atlantic Ocean !)
Earth Structure Earth was formed about 4.6 billion years ago, is the third terrestrial planet from the sun, supports life and is part of the solar system. The Earth is divided into three sections: Biosphere ( forms of life), the hydrosphere( fresh and salt water) and the internal structure (crust, mantle and core).
The Crust of the Earth Makes up 0.5% of Earth’s total mass and is divided into two parts: oceanic crust and continental crust. Oceanic crust is found under the ocean floor, is made of dense rocks such as basalt. It is about 7 kilometers (4 miles) thick. Continental crust, found under land masses, is made of less dense rocks such as granite. Its thickness varies between 10 and 75 kilometers (6 to 47 miles).
Earth's crust is divided into 15 major tectonic plates: North American Caribbean, Eurasian South American, Scotia, Antarctic, Arabian, African, Indian, Philippine, Australian, Pacific, Juan de Fuca, Cocos, Nazca Tectonic plates actually slide around on the mantle, causing earthquakes, mountain formation, continental drift, volcanoes, and other geologic activity on the crust.
The MOHO Moho, or Mohorovičić discontinuity, Is the boundary between the Earth’s crust and its mantle. The Moho lies at a depth of about 22 mi (35 km) below continents and about 4.5 mi (7 km) beneath the oceanic crust. Modern instruments have determined that the velocity of seismic waves increases rapidly at this boundary. The Moho was named for Andrija Mohorovičićseismic waveAndrija Mohorovičić
The Mantle Mantle lies between the core and crust; it is comprised of iron, magnesium, aluminum, and silicon-oxygen compounds. The Upper Mantle close to the crust is a hard rigid layer. (This layer and the Crust are called the Lithosphere) Under this is a flowing partly melted Mantle layer (known as the asthenosphere) The Lower Mantle, closest to the core is semi rigid and very hot.
Internal Structure of The Earth The Core: consists of a solid inner core of pure iron the size of the Moon, which is surrounded by an outer liquid core rich in iron and nickel roughly the size of Mars. Scientific knowledge of the deep earth comes from studying how seismic waves travel through the earth.
Mantle Core Crust Low-velocity zone Solid Outer core (liquid) Inner core (solid ) 35 km (21 mi.) avg., 1,200˚C 2,900km (1,800 mi.) 3,700˚C 5,200 km (3,100 mi.), 4,300˚C 10 to 65km 100 km 200 km 100 km (60 mi.) 200 km (120 mi.)
Movement of Heat within the Earth The Earth has internal processes: which alter and change the surface. The processes are a result of what is happening deep within the Earth’s interior. Two types of heat movement which happen inside the mantle are called: 1.Convection Cells: large volumes of heated rock move (like a wax blob in a lava lamp) 2.Mantle Plumes: mantle rock flows upward in a column (like smoke from a chimney) The heat convection causes the crustal plates to move.
Tectonic plate Collision between two continents Oceanic tectonic plate Spreading center Oceanic tectonic plate Ocean trench Plate movement Continental crust Oceanic crust Continental crust Mantle Inner core Hot outer core Two plates move towards each other. Hot material rising through the mantle Material cools as it reaches the outer mantle Cold dense material falls back through mantle
What are Tectonic Plates? Super heated rock or Convection cells and mantle plumes both move upward as heated material is displaced by cooler, sinking material. ( The most dense sink) These flows of energy cause movement of “tectonic plates” that lie on the crust Plates are about 60 miles thick and are Composed of continental and oceanic crust, and the outermost part of the mantle. ( a combo called the Lithosphere)
More about Plate Tectonics Tectonic plates move constantly, like large pieces of ice on lake surface Move about the rate of fingernails growing Throughout history, continents have drifted apart and joined together as plates move back and forth across Earth’s surface. Identical fossils found on more than one plate suggest they were once connected.
Can you find the North America Plate? We are here
Plate Tectonics- rock and roll Colliding, transforming and sub ducting plates produce mountains, faults and volcanoes and volcanic islands. Volcanoes and earthquakes are found near subducting plate boundaries (Oceanic under Continental plates) Two continental plates (Indian and Eurasian) colliding produced the Himalayan Mountain Range- which is constantly growing.
VolcanoesEarthquakes Earthquake and Volcaism Sites This area is called the RING OF FIRE
Boundaries Between Earth’s Plates Divergent Plate Boundaries: plates move in opposite directions Convergent Plate Boundaries: plates are pushed together by internal forces; forms a trench Transform Faults: occur where plates slide past one another; most are on the ocean floor
Earthquakes Earthquakes occur during plate movement on an existing fault, along plate boundaries and along the mid-oceanic ridges where the sea floor is spreading. Along fault boundaries, friction holds energy in place, and when the faults move – energy is released in all directions.
Earthquake ZONE The point of movement underground is called the focus of the earthquake. From the focus- seismic waves travel outward in all directions. Directly above the focus on the surface is called the epicenter.
Earthquake P and S Waves Earthquake P and S Waves Energy moves through the Earth in two different kinds of seismic or body waves. P waves and S waves P waves travel through Earth and are caused by expansion and contraction of bedrock. S waves are produced by vertical and horizontal movement near the upper surface layers Surface waves produce rolling and swaying motions and are slower than P and S waves.
Measuring Earthquakes The strength and magnitude of Earthquakes are commonly measured in two ways: The Richter Scale and the Mercalli Scale. The base 10 logarithmic Richter Scale measures magnitude or energy released using a seismograph. ( Scale range:0-10) Each number is 10x greater than the previous
The Mercalli Scale The Mercalli Intensity scale is a seismic scale used for measuring the damage of an earthquake. It measures the effects in a scale from I to 12. The lesser (1) being little or no effect and 12 being total destruction.
How Can We Reduce Earthquake Hazards? Examine historical records and make measurements to locate active fault zones Make maps to show high-risk areas Establish building codes for high-risk areas Try to predict where and when earthquakes will occur. Let’s move here !
Case Study Haiti 2010- The January earthquake was a catastrophic magnitude 7.0 quake that killed 200,000 people and injured 250,000. The capital Port-au-Prince and other cities were completely destroyed because of poor building codes.
Case Study 2 San Andreas Fault A transform fault line that extends 800 miles through California, forming a tectonic boundary between the Pacific and North American Plates. West of the fault is moving NW – East of the fault is moving SW. It moves 1.5 inches a year.
Volcanoes Occurs where magma (molten rock) reaches the Earth’s surface through a crack. Volcanic activity can release: pyroclastic flow of debris, ejecta (hot lava rock and ash), molten lava, and dangerous gases These gases may become concentrated in the atmosphere and become concentrated into sulfuric acid.
Volcanoes can be: active, intermittent, dormant or extinct volcanoes. 95% of all Volcanoes occur at subduction zones. Eruptions cause climate change by putting sulfate ions in the stratosphere which cause high clouds to occur – lowering temps. Volcanic eruptions can also make new volcanic islands like Hawaii.
extinct volcanoes magma reservoir central vent lithosphere Upwelling magma Volcano
Case Study Mt Saint Helens – 1980 eruption in Washington State which killed 57 people and destroyed wildlife and removed trees. Mount Pinatubo- 1991 eruption in the Philippines which lasted 9 hours, and spewed 18 million metric tons of sulfur dioxide into the stratosphere which encircled Earth. This caused a 1 degree C cooling of the entire planet.
Aftermath of Volcanoes Between 1985 and 1999: 561,000 people died from natural disasters; about 30% of these were from earthquakes and volcanic eruptions Benefits: scenery, lakes (Crater Lake in Oregon), fertile soil from weathering lava
How Can We Reduce Volcano Hazards? Land-use planning Better prediction of volcanic eruptions Evacuation plans
Minerals, Rocks and Soil The Earth’s crust is composed of minerals, rocks and a variety of soils. Elements form minerals and minerals form rocks. Through the processes of weathering and erosion, rocks change, break, and move. Minerals mix with organic material, forming the soil on which plants and animals rely.
Minerals Minerals are an element or inorganic compound that occurs naturally and is a solid (gold, silver, salt, quartz are all minerals found in the Earth) Common distinguishing characteristics include crystal structure and habit, hardness, lustre, diaphaneity, colour, streak, tenacity, cleavage, fracture,habit hardnesslustrediaphaneitystreakcleavage parting, and specific gravity.specific gravity
Three Major Types of Rocks 1.Igneous Rock: formed below or on Earth’s surface when magma (molten rock) wells up, cools, and hardens into rock (granite, lava rock) 2.Sedimentary Rock: formed from sediment when rocks are eroded, transported to another place, and deposited in water (sandstone) 3.Metamorphic Rock: rock is subjected to high temperature, high pressure, or chemically active fluids (coal, slate, marble)
Types of Soil Soil scientists describe soil types by how much sand, silt and clay are present. This is called texture.texture Soil Texture Triangles help figure out soil type:
Earth Processes There Processes that break down the Earth: such as geological changes based on energy from the sun, gravity, weathering and erosion. Erosion: material is dissolved, loosened, or worn away from one part of the Earth’s surface and THEN deposited in other places Wind can cause erosion as soil is blown from one area to another Human activities accelerate erosion
The Effects of Weathering Weathering: is a process that loosens material that can be eroded Two Types of Weathering: 1.Mechanical Weathering: large rock mass is broken into smaller fragments; Frost Wedging (water collects in pores of rocks, expands, and splits rock) 2.Chemical Weathering: chemical reactions decompose a mass of rock
Rock Cycle Rock Cycle Rock Rap Rocks are constantly exposed to changing conditions Interaction of processes that change rocks from one type to another is called the Rock Cycle Slowest of all Earth’s cycles; recycles material over millions of years