Science 10 Plate Tectonics PDF

SCIENCE 10 First Quarter – Lesson 1-2 PLATE TECTONICS– L.1 FOSSIL EVIDENCE: similar terrestrial species J. Tuzo Wilson’s Idea were found on many continents now separated by...

SCIENCE 10 First Quarter – Lesson 1-2 PLATE TECTONICS– L.1 FOSSIL EVIDENCE: similar terrestrial species J. Tuzo Wilson’s Idea were found on many continents now separated by oceans. Information collected by paleontologists. - he proposed that all lithosphere is broken into ANCIENT MOUNTAIN RANGES: the same separate sections called plates. His idea led to the sequence of rocks is found in North America, current theory of Plate Tectonics. Great Britain, and Norway. (The Appalachian Mountains) PLATE TECTONICS THEORY EVIDENCE OF ANCIENT GLACIERS: Glaciers 1. CONTINENTAL DRIFT: carve the rock as they move; Scientists can - Alfred Wegener proposed the hypothesis of determine the direction of movement (notice the continental drift in 1911. He gathered information direction of movement noted in South America); from many different sources and used it as As South America sits today; the pattern would evidence for his hypothesis. not make sense (glaciers do not move from sea Continental Drift Hypothesis: The level to higher elevations). continental Drift Hypothesis proposes that 2. SEAFLOOR SPREADING: the continents were assembled to form the - In the 1963, Harry Hess developed the idea of super continent Pangea. It moved through seafloor spreading to explain the seafloor’s time. (Fit of the continents, fossil evidence, formation. Continental movement is the result of ancient mountain ranges, and past climate ocean floor movement. evidence.) *PANGEA: occurred 225 million Plate Tectonics: years ago. ❖ The Earth’s crust is divided into 7 World Plates: the outer shell of the Earth, major plates which are moved in the lithosphere, is broken up into tectonic various directions. plates. The seven major plates are the: ❖ This plate motion causes them to a. African Plate collide, pull apart, or scrape against b. Antarctic Plate each other. c. Eurasian Plate ❖ Each type of interaction causes a d. Indo-Australian Plate characteristic set of Earth structures e. North American Plate or “tectonic” features. f. Pacific Plate ❖ The word, tectonic, refers to the g. South American Plate deformation of the crust as a Plates that interact for the formation of our consequence of plate interaction. country, the Philippines: ❖ The tectonic platers are made of rigid 1. EURASIAN lithosphere. The lithosphere is 2. INDO-AUSTRALIAN made up of the crust and the upper 3. PHILIPPINE part of the mantle. Below the *Explains that the Earth’s Lithosphere is broken into lithosphere (which makes up the distinct units that move as a coherent package. Where the tectonic plates) is the tectonic plates meet, produces distinct physical asthenosphere. characteristics on the Earth’s Surface. Plate Movement: “plates” of lithosphere are moved around by the underlying hot mantle EVIDENCES OF CONTINENTAL DRIFT convection cells. THEORY ❖ Arthur Holmes (1890-1965, FIT OF CONTINENTS: Antonio Snider-Pelligrini England): One of the few (1858): a geographer cut out a map of Africa and Anglophone geologists who South America suggesting they were connected at supported the continental drift one time. Other physical evidence based on theory. Proposed that the mantle had observation was used by Wegener. FIRST QUARTER W.T SCIENCE 10 First Quarter – Lesson 1-2 convection currents, which moved - Continental to Oceanic Crust Collision: the continents. called subduction. (Volcanoes) Seafloor Features: mid-oceanic ridges, Subduction: oceanic lithosphere subducts trenches. Volcanism adjacent to trenches, underneath the continental lithosphere. seamounts, fracture zones. Oceanic lithosphere heats and dehydrates as it subsides. The melt rises forming EVIDENCES OF SEAFLOOR SPREADING volcanism. - Oceanic to Oceanic Plate Collision: when THEORY two oceanic plates collide, one runs over the REMANENT MAGENTISM: the magnetization of other which causes it to sink into the mantle rocks that form in the presence of an external forming a subduction zone; the oceanic plate magnetic field. When molten material containing melts. The subducting plate is bent downward the mineral magnetite (Fe3O4) is extruded to form a very deep depression in the ocean upward from the mantle (for example, in a floor called a trench. E.g. is the Mariana volcanic eruption) and solidifies in the Earth’s Trench - 11 km deep magnetic field. Thus, the newly formed seafloor C. TRANSFORM BOUNDARIES: forms fault rock preserves the magnetic record at that time. lines and rift valleys - Where plates slide past each other. E.g. is the 2 TYPES OF CRUST/PLATE San Andreas Fault 1. CONTINENTAL CRUST - Are the boundaries between two plates that are - Less dense sliding horizontally past one another. Creation - Granite Rock of HotSpots – Hot magma plume. E.g. is - 20-50km THICK located at Hawaii Island (Kawai, Oahu, Maui) - Older and Reunion Island 2. OCEANIC CRUST - More dense - Basalt Rock (1/28 age of continental rocks) ; *Seafloor feature was discovered using sonar. Echo (basalt is a volcanic rock with a mafic sounding was used to map the seafloor. composition, higher percentages of iron and *Iron-rich rocks are magnetized as they cool to the current magnesium, lower percentages of silicon and magnetic field. oxygen) - 5-10km THIN *Pacific Ring of Fire - Younger - Youngest at ridge, older away from the ridge *Volcanoes are formed by: subduction-rifting-hotspots (old-away; young-near) - Mirror image across the ridge *Hotspots Volcanoes: hot mantle plumes breaching the *Formed through Convection Process surface in the middle of a tectonic plate. 3 TYPES OF PLATE BOUNDARIES 3 TYPES OF ROCKS A. DIVERGENT BOUNDARIES: forms ridges A. IGNEOUS ROCK: - Spreading Ridges: as plates move apart, new - Word means “fiery” material is erupted to fill the gap. - This rock is formed when molten (melted) rock cools and solidifies. - Sometimes magma cools slowly underneath the Earth’s Surface, this forms Intrusive Igneous B. CONVERGENT BOUNDARIES: forms Rocks like Granite. Volcanoes, Mountains, Trenches - Other times lava cools when lava cools at the - Continental to Continental Collision: slow surface when a volcanic eruption occurs. This motion, ½ billion years ago; Forms mountains forms Extrusive Igneous Rocks like Tuff, like the European Alps, Swiss Alps, Himalayas. Obsidian, and Pumice. (Mountains) – plates pushed together. - Igneous rocks make up about 95% of the Earth’s crust. FIRST QUARTER W.T SCIENCE 10 First Quarter – Lesson 1-2 B. SEDIMENTARY ROCK: - Sediment are small particles of sand, mud, and organic material that settle to the bottom of water or land areas; often lakes or oceans. - Formed when sediment accumulates overtime in the deposits that forms layers. These layers are becomes squeezed and compressed overtime until they can solidate into a rock. - Types of rocks in which fossils may be found. It can preserve plant or animal remains THE CRUST - Some examples of sedimentary rocks are; CRUST: Limestone, Shale and Sandstone. C. METAMORPHIC ROCK: - The shallowest layer of the Earth. - Meta morph means to change form, and these - The most heterogeneous layer in the Earth. rocks is rock that is changed by extreme heat - The crust is on average 22 km thick for continents pressure. and 10km thick beneath oceans; however, it varies - These rocks can be formed by being deep under from just a few km to over 70 km globally. the Earth where pressure and temperature are - The boundary between the crust and the mantle is high or when rock near the surface is heated up by the movement of tectonic plates or magma. mostly chemical. They have different - Different types of rocks become different types compositions. of metamorphic rock when exposed to heat and - This boundary is referred to as the Mohorovicic pressure. Ex: (1) Shale becomes Slate, (2) Discontinuity or “Moho”. Sandstone becomes Quartzite, and (3) - It was discovered in 1910 by the Croatian Limestone becomes Marble. seismologist, Andrija Mohorovicic. - This is where we live. - The Earth’s crust is made out of: Continental Crust EARTH’S INTERIOR– L.2 and Oceanic Crust. The Earth is made up of 3 main layers: - The outermost “skin” of Earth with variable thickness. 1. CORE: Inner and Outer Core 2. MANTLE: Upper and Lower Mantle THE MANTLE 3. CRUST - Exists from the bottom of the crust to a depth of There are five discontinuities inside the earth: 2891 km radius of 3480 km – Gutenburg Discontinuity. 1. Conrad Discontinuity: Transition zone between - It is further subdivided into: SIAL and SIMA. The uppermost mantle (crust to 400km depth) 2. Mohorovicic Discontinuity: Transition zone The transition zone (400-700km depth) between the Crust and Mantle. The mid-mantle (700 to – 2650km depth) 3. Repiti Discontinuity: Transition zone between The lowermost mantle (2650-2891km Outer mantle and Inner mantle. depth) - The uppermost mantle is composed dominantly 4. Gutenberg Discontinuity: Transition zone of olivine; lesser components include pyroxene, between Mantle and Core. enstatite, and garnet. 5. Lehman Discontinuity: Transition zone - Solid rock layer between the crust and the core. between Outer core and Inner core. - 2885km THICK, the mantle is 82% of Earth’s volume. - Mantle composition – Ultramafic rock called periodite. FIRST QUARTER W.T SCIENCE 10 First Quarter – Lesson 1-2 - Hot mantle rises, cold mantle sinks. Magma: molten rock beneath the surface. Lava: molten rock at the surface. EARTH’S CORE C. VOLATILES: materials that turn into gas at the - Owing to the great pressure inside the Earth’s core surface temps. is actually freezing as the Earth gradually cools. H20, CO2, CH4, and SO2 - The boundary between liquid outer core and the Volatiles are released from volcanic solid inner core occurs at a radius of about eruptions. 1220km – Lehman Discontinuity, after Inge Lehman from Denmark. *MECHANICAL LAYERS: Lithosphere, Asthenosphere, - The boundary between the mantle and outer core and Mesosphere is sharp. *CONVECTION: the asthenosphere enables tectonic - The change in density across the core-mantle processes – plate tectonics. boundary is greater than that at the Earth’s surface. EARTHQUAKES - The viscosity of the outer core is similar to that of EARTHQUAKE CLUES: earthquake energy transmitted as water, it flows km per year and creates the Earth’s seismic waves that passes through Earth. Wave velocity magnetic field. changes with density. Velocity changes give depth of layer - Outer Core is the most homogenous part of the changes. Earth. Mostly an alloy of iron and nickel in liquid form. - Some energy bounces off harder layers called - Inner Core has solid iron-nickel alloy, radius of reflection. 1220km, with the density of 13 g/cm^3 - Some energy travels through but gets bent, - As the core freezes, latent heat is released; this changing the direction the wave is traveling called heat causes the outer core to convect and so refraction. generates a magnetic field. - Some energy is absorbed as it encounters materials called attenuation LITHOSPHERE - The lithosphere is the uppermost 50-100km of the *CHANGES WITH DEPTH: pressure and temperature Earth. HOW DO WE KNOW WHAT THE EARTH IS MADE - There is not a strict boundary between the OF? lithosphere and the asthenosphere as there is between the crust and mantle. - Geophysical surveys: seismic, gravity, magnetics, - It consists of both crust and upper parts of electrical, geodesy. Acquisition: liquid, air, sea, and mantle. satellite. Geological Survey: fieldwork, boreholes, - It behaves, like a solid, over very long time mines. periods. WAVES ASTHENOSPHERE ELASTIC WAVES – BODY WAVES: inside the Earth - The asthenosphere exists between depths of - Body Waves: Body waves are waves that travel 100-200km. through the Earth's interior. First one to get - It is the weakest part of the mantle. recorded in the seismograph. - It is solid over short time scales, but behaves like a *P-Waves: side waves, can travel through fluid over millions of years. liquids. - The asthenosphere decouples the lithosphere *S-Waves: ups and downs, can’t travel through (tectonic plates) from the rest of the mantle. liquids. EARTH’S MATERIALS A. METALS: solid made of metallic elements. B. MELTS: rocks that have been heated to a liquid. FIRST QUARTER W.T SCIENCE 10 First Quarter – Lesson 1-2 - Van Allen Belts – two belts in the inner magnetic field where high energy cosmic rays are trapped. Protects us from solar radiation. - Earth’s magnetic field plays a vital role in the development of Plate Tectonics Theory. AURORAE - Some ions escape – Van Allen Belts These ions are pulled to the magnetic poles. The ions create light in the upper atmosphere. ELASTIC WAVES – SURFACE WAVES: above the Earth - Spectacular aurora follows solar flares. - Surface Waves: travel more slowly through Earth Aurora Borealis – Northern Lights material at the planet's surface and are Aurora Australis – Southern Lights predominantly lower frequency than body waves. Last to be recorded in the seismograph. SUMMARY/SYNTHESIS The Earth is composed of three major layers: the SEISMIC WAVES: Rayleigh and Love Waves crust, mantle, and core which is subdivided into outer and inner core. The crust is the outermost - Seismic Waves are caused by the sudden and thinnest layer of the Earth. The mantle is the movement of materials within the Earth, such as middle layer of the Earth. It makes most of the slip along a fault during an earthquake. Earth’s volume and mass. - R and L Waves; Their amplitude diminishes with The crust and a part of the upper mantle make the depth; they have large amplitudes and are up the lithosphere. The lithosphere is slower than body waves. These are dispersive subdivided into portions called lithospheric waves (large periods are faster.) plates. Rayleigh Waves: ups and downs, spread out the most The asthenosphere is the weak layer of the Love Waves: sideways, moves faster mantle on which the lithosphere floats. The outer core is made up of molten material *Factors affect Seismic Waves: and accounts for the Earth’s magnetic field. The inner core is the deepest layer of the Earth. It - Distance: farther = more attenuation density: higher = faster is made up of solid nickel and iron. The temperature: colder = faster temperature in the inner core reaches as high as - Liquid vs Solid 5000o C. solid = faster; p-waves and s-waves The speed, reflection and refraction properties liquid = slower; no s-waves of seismic waves are used by scientists to study the - Angle of incidence - controls how much is structure and composition of the Earth’s interior. reflected and how much is absorbed vertical arrangement of layers. - Controls the resultant direction of travel. EARTH’S MAGNETIC FIELD - Like a bar magnet, Earth’s magnetic field is a dipole. (Has both a N and S pole) - Solar wind contains electromagnetic particles that are deflected by Earth’s Field. These particles distort the shape of Earth’s magnetic field in space. FIRST QUARTER W.T