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Summary from Science Framework
Standard Set 3.
Dynamic Earth Processes
·See Framework & Standard
The earth sciences use concepts, principles, and theories from the physical sciences and mathematics and often draw on facts and information from the biological sciences. To understand Earth's magnetic field and magnetic patterns of the sea floor, students will need to recall, or in some cases learn, the basics of magnetism. To understand circulation in the atmosphere, hydrosphere, and lithosphere, students should know about convection, density and buoyancy, and the Coriolis effect. Earthquake epicenters are located by using geometry. To understand the formation of igneous and sedimentary minerals, students must master concepts related to crystallization and solution chemistry.
Because students in grades nine through twelve may take earth science before they study chemistry or physics, some background information from the physical sciences needs to be introduced in sufficient detail. From standards presented earlier, students should know about plate tectonics as a driving force that shapes Earth's surface. They should know that evidence supporting plate tectonics includes the shape of the continents, the global distribution of fossils and rock types, and the location of earthquakes and volcanoes. They should also understand that plates float on a hot, though mostly solid, slowly convecting mantle. They should be familiar with basic characteristics of volcanoes and earthquakes and the resulting changes in features of Earth's surface from volcanic and earthquake activity.
excerpt from:
Chapter Five: Earth Science, Investigation and Experimentation.
Science Framework for California Public Schools: Kindergarten Through Grade Twelve, 2004.
California Department of Education.
Acquired from online source on July 13, 2007.
· See full Framework
Standard Set 3.
Dynamic Earth Processes
·See Framework & Standard
The earth sciences use concepts, principles, and theories from the physical sciences and mathematics and often draw on facts and information from the biological sciences. To understand Earth's magnetic field and magnetic patterns of the sea floor, students will need to recall, or in some cases learn, the basics of magnetism. To understand circulation in the atmosphere, hydrosphere, and lithosphere, students should know about convection, density and buoyancy, and the Coriolis effect. Earthquake epicenters are located by using geometry. To understand the formation of igneous and sedimentary minerals, students must master concepts related to crystallization and solution chemistry.
Because students in grades nine through twelve may take earth science before they study chemistry or physics, some background information from the physical sciences needs to be introduced in sufficient detail. From standards presented earlier, students should know about plate tectonics as a driving force that shapes Earth's surface. They should know that evidence supporting plate tectonics includes the shape of the continents, the global distribution of fossils and rock types, and the location of earthquakes and volcanoes. They should also understand that plates float on a hot, though mostly solid, slowly convecting mantle. They should be familiar with basic characteristics of volcanoes and earthquakes and the resulting changes in features of Earth's surface from volcanic and earthquake activity.
excerpt from:
Chapter Five: Earth Science, Investigation and Experimentation.
Science Framework for California Public Schools: Kindergarten Through Grade Twelve, 2004.
California Department of Education.
Acquired from online source on July 13, 2007.
· See full Framework
Overview
The Earth's surface reshapes itself in a big way. Plate tectonics is the overarching conceptual understanding of how and why the Earth's surface continues to undergo large-scale deformation and change. Processes related to plate tectonics control and shape the large-scale features of the landscape - land, sea and mountains. It controls the distribution of geologic hazards such as earthquakes and volcanoes, and the original and shifted location of natural resources such as petroleum and metals. The very climate, geography and life at any particular place and geologic time is largey influenced by plate tectonics. Of the planets in the solar system are tectonically activity, Earth is the only one dominated by the motion of plates.
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Overview and key concepts
Standard 3b: Students know the principal structures that form at the three different kinds of plate boundaries.
Note: Types of plate boundaries (convergent, divergent and transform) may be confused with types of continental margins (active and passive).
Standard 3a: Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.
Supporting materials
Causes of plate motion
The motive Convection (motion) inside the Earth
Reconstruction and forecast
The action of plate tectonics has changed shape of the Earht's surface, land, sea mountains, resources weather.
Activity http://www.nasa.gov/centers/jpl/images/content/151456main_gps-warning-browse.jpg http://commons.wikimedia.org/wiki/Image:Tectonic_plates.png http://emvc.geol.ucsb.edu/downloads.php http://en.wikipedia.org/wiki/Transform_fault http://en.wikipedia.org/wiki/Supercontinent_cycle Review items
- Definition of tectonics and plate tectonics
Note: The concept of plate tectonics may be difficult to pin down. There may be reference to plate tectonics as very different things - force, scientific theory, object, concept, or process.
• What is plate tectonics?
• Scientific "theory" vs. conjecture
- How the concept of continental drift evolved into plate tectonics
Note: The concepts of continental drift and plate tectonics concepts may not be clearly distinguished.
• Wegener's concept of continental drift
• The circumstantial fit of the continents
• Matching patterns that are now widely separated
• Wandering land better option than "polar wander"
• Plate tectonics explains how and why plate move
Standard 3b: Students know the principal structures that form at the three different kinds of plate boundaries.
Note: Types of plate boundaries (convergent, divergent and transform) may be confused with types of continental margins (active and passive).
- Three kinds of plate boundaries (plate margins):
• Divergent plate margins
• Convergent plate margins
• Transform margins
Note: All "strike-slip" faults are not "transform" faults
- Two kinds of continental margins:
• Active
• Passive
- Two ways of defining the internal layers of the Earth:
• By composition
• By how it responds to stress (having a force exerted on it)
Standard 3a: Students know features of the ocean floor (magnetic patterns, age, and sea-floor topography) provide evidence of plate tectonics.
- Key process: Seafloor-spreading grows new seafloor (takes place at midocean ridges)
• The process of seafloor spreading
• What makes seafloor spreading take place
- Key process: Subduction consumes and destroys seafloor (takes place at subduction zones)
- How we know that plates move - direct evidence
Note: Although most explanations concentrate on the logic and development of the plate tectonic concept over time, acceptance of the potential consequences no longer depends on understanding the full explanation because we can now observe the plates actually moving.
• GPS measurements
• Displacement after earthquakes
- How we know that plates move - circumstantial evidence
Note: Until recently, most evidence did not directly show that plates move, but many previously unexplained observations were consistent and conveniently explained by plate tectonics. The acceptance of the plate tectonics model of how the Earth works was a little like making making a court decision - multiple and consistent lines of supporting circumstantial evidence made a strong enough case to sway the jury to accept plate tectonics.
Note: Although the magnetic pattern of the seafloor was one of the key pieces of evidence moving forward the acceptance of plate tectonics as an overarching theory, it is difficult for many to understand why it is such a compelling piece of evidence.
Seafloor:
- Topography
- Age pattern
- Magnetic pattern
- Hotspot volcanic chains (Hawaii)
Standard 3f: Students know the explanation for the location and properties of volcanoes that are due to hot spots and the explanation for those that are due to subduction.
Land:
- Apparent polar wander
- Matching features that are separated by great distances
Both land and sea:
- Earthquakes
Standard 3d: Students know why and how earthquakes occur and the scales used to measure their intensity and magnitude.
- Volcanoes
Standard 3e: Students know there are two kinds of volcanoes: one kind with violent eruptions producing steep slopes and the other kind with voluminous lava flows producing gentle slopes.
- Topography
Supporting materials
- Magnetic field
• The Earth's magnetic field
• How rocks are magnetized
• The seafloor magnetic pattern as evidence for plate tectonics
- How rocks are dated
• Using the seafloor magnetic pattern to date the seafloor
• Radiometric dating
Assigning ages in numbers of years.
• Relative dating methods
Knowing which rock is older without knowing exactly how old in numbers of years.
- Earthquakes
• What's an earthquake?
• How earthquakes are located by triangulation ?
• Earthquake hazards ?
- Volcanoes
• Types of volcanoes and tectonic setting Standard 3c: Students know how to explain the properties of rocks based on the physical and chemical conditions in which they formed, including plate tectonic processes.
• Types of rocks and tectonic setting
• Temperature and pressure inside the Earth
• How crystals form
• Partial melting (fractional crystallization)
• Boewn's reaction series
• Chemical solutions
The motive
The action of plate tectonics has changed shape of the Earht's surface, land, sea mountains, resources weather.
- Paleogeographic reconstruction
[Flash]
Activity http://www.nasa.gov/centers/jpl/images/content/151456main_gps-warning-browse.jpg http://commons.wikimedia.org/wiki/Image:Tectonic_plates.png http://emvc.geol.ucsb.edu/downloads.php http://en.wikipedia.org/wiki/Transform_fault http://en.wikipedia.org/wiki/Supercontinent_cycle Review items
- Physics
- Density
- Buoyancy
- Convection
- Coriolis force
- Magnetism
- Chemistry
- Crystallization of solids
- Solution chemistry
- Biological sciences
- Mathematics
- Geometry - triangulation
3. Plate tectonics operating over geologic time, changed patterns of land, sea, mountains (As basis for understanding concept)
3.a. know Ocean floor features provide evidence of plate tectonics
- Magnetic patterns
- Age
- Sea-floor topography
Paragraph 1
- Much evidence for continental drift from seafloor (rather than continents)
- Longest topographic feature in world, mid-oceanic ridge system
- Chain of volcanoes/rift valleys
- 4X10^5 miles long, rings planet like seams of a giant baseball
- Mid-Atlantic Ridge, located halfway between and parallel to coasts of
- Europe and Africa
- North and South America
- Ridge system made from youngest rock on ocean floor
- Floor gets progressively older, symmetrically, on both sides
- No portion of ocean floor is more than 200 million years old
- Sediment thin on/near ridge
- Sediment found away from ridge thickens, contains progressively older fossils
- Phenomenon a symmetrically
Paragraph 2
- Mapping magnetic field anywhere across ridge system produces
- Pattern of high and low fields in almost perfect symmetrical stripes
- Scientific detective work inferred, "zebra stripes" arose because
- Lava erupted/cooled, locking into rx residual magnetic field
- Direction matched Earth's field when cooling took place
- Magnetic field near rx is sum of residual field, Earth's present-day field
- Near lavas that cooled during times of normal polarity
- Residual field points along Earth's field; total field is high
- Near lavas that cooled during times of reversed polarity
- Residual field points counter to Earth's field; total field is low
- Stripes provide strong support for idea of seafloor spreading
- Lava in stripes can be dated independently
- Regions of reversed polarity correspond w/ times of known geomagnetic field reversals
- Theory states:
- New seafloor created by volcanic eruptions at mid-oceanic ridge
- Erupted material continuously spreads out convectively
- Opens, creates ocean basin
- At some continental margins deep ocean trenches mark places where
- Oldest ocean floor sinks back into mantle
- Completes the convective cycle
- Continental drift, seafloor spreading form the modern theory of plate tectonics
3.b. know Principal structures that form at the three different kinds of plate boundaries
Paragraph 1
- Three types of plate boundaries, classified according to their relative motions
- Divergent, convergent, transform (or parallel slip)
- Divergent boundaries occur where plates are spreading apart
- Young divergence characterized by thin or thinning crust/rift valleys
- If divergence goes on long enough, mid-ocean ridges develop
- Mid-Atlantic ridge
- East Pacific Rise
- Convergent boundaries occur where plates are moving toward each other
- Oceanic material that is dense enough, may sink back into mantle, produce trench
- Process known as subduction
- Sinking material may partially melt, producing volcanic island arcs
- Aleutian Islands, Japan
- If subduction of denser oceanic crust occurs underneath a continent
- Volcanic mountain chain formed
- Andes, Cascades
- When two plates collide/both too light to subduct
- One continent crashes into another
- Crust is crumpled, up-lifted producing mountain chains
- Himalayas (young), Appalachians (old)
- Transform (or parallel slip) boundary where two plates move laterally by each other, parallel to boundary
- San Andreas fault, CA
- Boundary between North American/Pacific plates
- Fault runs from Gulf of CA NW to Mendocino County in N CA
3.c. know Explain properties of rx based on physical/chemical conditions in which they formed, including plate tectonic processes
Paragraph 1
- Rocks classified according to their
- Chemical compositions
- Textures
- Composition reflects chemical constituents available when rock formed
- Texture indicates conditions of temp/pressure under which rock formed
- Igneous rx, cooled from molten material, interlocking crystalline textures
- Sedimentary rx, (many have) fragmental textures
- Whether formed from cooling magma, created by deposits of sediment grains, transformed by heat/pressure
- Each rock possesses identifying properties that reflect its origin
Paragraph 2
- Plate tectonic processes directly/indirectly control distribution of rock types
- E.g., subduction takes rx from close to surface, drags them down to depths
- Subjected to increased pressures/temps
- Tectonic processes uplift rx, so exposed to lower temps/pressures, weathering
3.d. know Earthquakes occur, scales used to measure
Paragraph 1
- Most earthquakes caused by lithospheric plates moving against each other
- Earth's brittle crust breaks episodically, stick-and-slip manner
- Plate tectonic stresses build up until enough energy stored to overcome frictional forces at plate boundaries
- Magnitude of earthquakes (e.g., Richter scale) measure of wave amplitudes
- Magnitude depends on amount of energy stored as elastic strain, then released
- Magnitude scales logarithmic, increase of one point on scale represents
- Wave amplitude increase by factor of ten
- Energy increase by factor of (about) thirty
- Earthquake's intensity (on modified Mercalli scale) subjective, valuable
- Measure of how strong earthquake felt
- Measure of how much damage at any given location
3.e. know two kinds volcanoes:
Paragraph 1
- Violence of volcanic eruptions function of viscosity of lava that erupted
- All magmas contain dissolved volatiles (gases) that expand, rise buoyantly as magma rises to surface-much like bubbles in bottle of soda
- Fluid lavas allow gases to bubble away relatively harmlessly
- Viscous lavas trap gas, large pressures build up, system explodes
- Temperature, composition determine viscosity of magma
- Magma at cool temperatures, with high silica content very viscous
- Rhyolitic, andesitic lavas examples of lavas w/ high viscosity
- Erupt violently, scattering volcanic fragments, ash widely
- Viscous lava, which does not flow very far, builds steep-sided volcanoes
- Other lavas, such as basaltic, relatively fluid, erupt quietly
- Producing great flows of lava, build gently sloping deposits
- Shield volcanoes
Review
Magnetism