Plate Tectonics Unit LO Describe forces that shape

Plate Tectonics Unit:

LO: Describe forces that shape the surface of the earth. SLE: Meet or exceed NGSS Checkpoint Quiz on Weathering, Erosion, and Deposition: 1. ) Is the picture to the upper right an example of chemical or physical weathering? How do you know? 2. ) List three main causes of physical weathering. 3. ) After a storm hits a beach, a sand bar is formed 200 m offshore. Is this formation of a sand bar an example of weathering, erosion, deposition or a combination of any or all of these? Explain your response. 4. ) In the picture to the lower right, where would you expect deposition to occur?

Composition of the Earth: Layers of the Earth: 1. Crust: 5 -100 km thick. a. Oceanic crust: thin and more dense, mostly basalt b. Continental crust: thicker and less dense, made up of more granite than oceanic crust

Layers, Continued: 2. mantle: made of molten (melted rock), very thick, 2, 900 km, and likely to have convection currents. 3. Outer Core: molten iron, 2, 200 km thick 4. Inner Core: solid but very hot iron, 1, 230 km thick The core makes up 33% of Earth’s total mass

Tectonic Plates: Because of convection currents in the mantle, plates of the earth’s crust move around as they “float” on the mantle. Over many millions of years, the location of the oceans and continents have changed dramatically, and surface features like valleys and mountain ranges are continually created and destroyed.

Wegener’s Theory of Continental Drift: In 1910, a German scientist named Alfred Wegener proposed that the continents had, in the very distant past, been joined together in one supercontinent he called Pangea, and had since drifted apart into separate continents. He called this theory Continental Drift.

Wegener’s arguments in support of his theory: 1. Evidence from landforms: • Continents along the Atlantic Ocean appear to fit together like puzzle pieces. • Mountain ranges in South Africa match up with mountains in South America. • Coal deposits in Europe match up with coal deposits in North America.

2. Evidence from fossils: • Fossils of the same species of land animals and land plants had been found on different continents; they could not have crossed oceans. • Fossils of tropical plants were found on the island of Spitsbergen, which is well north of the Arctic Circle. Wegner proposed that this island had once been close to the equator. • Evidence of glaciers had been found in South Africa, which currently has a subtropical climate. Wegner thought South Africa must have been much farther south millions of years ago.

Unfortunately, no one believed Wegener at the time. His evidence was not totally convincing, and he could not explain what force could cause whole continents to move.

Plate Tectonics: Wegener was Right! Starting in the 1960’s, as scientists started mapping the ocean floor, they discovered that the ocean floor was spreading out along the Mid-Ocean Ridge. This very easily explained how continents could move.

How Sea-Floor Spreading Works:

Evidence for Sea-Floor Spreading: 1. 2. 3. Rock samples from the ocean floor close to the mid-ocean ridge are younger than rock samples farther away. Magma can actually be observed oozing up from the mid-ocean ridge, and cooling into rock. Iron samples from the ocean floor alternate their patterns, showing that some parts of the ocean floor were formed at times when the magnetic poles were reversed.

Subduction at Deep Ocean Trenches:

The Ultimate Cause of Plate Movement? Convection!

Tectonic Plates of the Earth:

Types of Plate Boundaries:

LO: Describe theory of plate tectonics SLE: Meet or exceed NGSS Checkpoint Quiz on Plate Tectonics: 1. When Wegener proposed the idea that continents are “drifting” in 1912, no one believed him. Why not? 2. Describe two observations that support the modern theory of plate tectonics. 3. Where on the ocean floor can the newest rock be found? Why? 4. List one surface feature of the earth that is the result of moving plates. 5. List and describe three kinds of plate boundaries (diagram OK).

LO: Describe theory of plate tectonics SLE: Meet or exceed NGSS Checkpoint Quiz on Plate Tectonics: 1. Describe the process of sea-floor spreading (diagram OK). 2. Give one piece of evidence for theory of plate tectonics. 3. What causes the formation of most mountain ranges? 4. Name three types of plate boundaries, and describe the movement of plates along each one (diagrams OK) 5. Draw 3 types of faults. For each type, draw arrows to show the rock moves along that type of fault.

The Effects of Tectonic Plate Movement on Earth’s Surface : Plate movement causes the earth’s surface to deform (noun: deformation): layers of rock bend or break because of the stress placed on them.

Main Types of Stress: Compression: When two plates are squeezed together. Tension: When two plates are pulled apart. Shearing: when two plates are pulled past one another.

Folds: Folding is the bending of rock layers due to one of these three types of stress. Types of folds: Anticlines: upward-pointing folds. Synclines: Downwardpointing folds. Monocline: A step-like fold in which both ends are horizontal.

Faults: Faults are regions where rock areas break and slide past each other. When faults are not totally vertical, the upper part is called the hanging wall and the lower part is called the footwall.

Types of Faults:

Plate Tectonics and Mountain Formation: The motion of Earth’s plates causes mountains to form, mostly at plate boundaries. The type of mountains that are formed depends on what type of plate boundary it is.

Types of mountains: Folded Mountains: When plates are squeezed together and pushed upward. These are usually formed at convergent boundaries. Fault-Block Mountains: When plates move apart and one section of rock drops down relative to other sections. (These tend to be smaller mountains. ) Volcanic Mountains: Formed by volcanic eruptions, usually near subduction zones.

Homework: LO: Describe effects of the movement of tectonic plates. SLE: Articulate ideas clearly and effectively. 1. Read p. 112 -118 2. Answer review questions on p. 119

LO: Describe motion of the earth along faults. SLE: Meet or exceed NGSS Checkpoint Quiz on Rock Movement: Draw three kinds of faults. For each fault, draw arrows to show the earth moves along that fault. Also mention the type of stress experienced at each type of fault: (6 points) 1. 2. 3.

Earthquakes: Where earthquakes occur: Most earthquakes occur at or near plate boundaries. The crust moves more often in these places, and stress is more likely to build up there.

The cause of earthquakes: Rock at plate boundaries or along faults will stretch as sections move past one another, but eventually so much pressure builds up that the rock breaks and snaps back (like a rubber band), which releases waves of energy. The sudden snapping back of rock is called elastic rebound. Elastic rebound

Seismic waves: Seismic waves are energy waves caused by rock vibrations along a fault. There are 3 kinds of seismic waves: 1. Primary (P): The first to arrive (the fastest). They compress and expand like a Slinky. 2. Secondary (S): They come after primary waves. They move from side to side and up and down. S waves, unlike P waves, can not travel through liquids. 3. Surface waves: P or S waves that have reached the surface. These are the waves that cause the most damage, although they are slower than the other two.

How earthquake strength is measured: Earthquakes are detected, located and their strength measured by a machine called a seismometer. They record the movement of the earth using a needle; the more the ground shakes, the more the needle does, too.

Earthquake measuring scales: 1. Mercalli Scale: Developed early in the 20 th century, this scale does not measure the energy precisely, but records the amount of damage that has been done. 2. Richter Scale: Developed in 1930, it measures the strength of an earthquake according to how much motion the nearest seismometer has recorded. This could change depending on how far away from the earthquake the seismometer is.

3. Moment Magnitude Scale: This is the scale used today. It measures the total energy produced by the earthquake, not the results of the earthquake. In this scale, each magnitude is ten times larger than the next lowest number.

Epicenter vs. Focus: The location below ground where the earthquake begins. This can be many Km below the surface. Epicenter: The first location on the surface where the earthquake can be felt.

Homework: LO: Describe cause and effects of earthquakes. SLE: Meet or exceed NGSS. Read through your notes on earthquakes. Then do one of the following: 1. Write a 5 -sentence paragraph that describes what causes earthquakes. 2. Draw a labeled diagram that describes what causes earthquakes. 3. Take a quiz on the cause and effects of earthquakes on Wednesday. (This will be your only option if you don’t do options 1 or 2). No matter which option you choose, include information about the role of plate tectonic motion, seismic waves, and stress.

LO: Identify, describe causes and effects of earthquakes SLE: Articulate ideas clearly, effectively and creatively. Earthquake paragraph: Write a 7 -9 sentence paragraph (including topic sentence) that describes the Cascadia Fault. Include information about where the fault is located, what would cause an earthquake at this fault, and what the effects of a “megathrust” earthquake might be on cities in the Pacific Northwest. (No hysteria or fear-mongering, please. ) Also include one or two things that people are doing to prepare for a major earthquake along the Cascadia Fault.

LO: Describe the cause and effects of earthquakes. SLE: Meet or exceed NGSS Checkpoint Quiz on Earthquakes: 1. What causes earthquakes? 2. Where on on Earth are earthquakes most likely to occur? 3. What device is used to measure the amount of energy produced by earthquakes? 4. What’s the difference between an epicenter and a focus of an earthquake? 5. What measurement scale is used to measure earthquake energy in the United States?

Earthquake Safety: The likelihood of experiencing an earthquake depends on where you are. If you live near a plate boundary, your earthquake hazard level is higher.

Forecasting Earthquakes: Predicting when and where the next earthquake will occur is very difficult. However, scientists sometimes try the Gap Hypothesis: Areas along faults that haven’t had an earthquake in a while are more likely to experience a strong one in the future.

Earthquake-Proof Building Design Features: Mass Damper: A weight placed on the roof to keep the building from swaying. Shear wall: braces in walls to prevent them from tearing in half. Active tendon system: Shock absorbers built into the frame of the building. Base isolators: Felxible layers of material built into the foundation of the building. Pilings: In soft soil, long posts underground attached to the bedrock below the surface. Cross braces: To keep the building from shaking apart. Flexible pipes: To prevent fires from gas leaks.

What to do during an earthquake: • Drop, cover and hold • Wait 100 seconds in case of immediate aftershocks • Quickly and calmly exit the building • Gather in an open area and await instructions from trusted adults.

Homework: LO: Identify and describe earthquake-resistant design features SLE: Work independently 1. Read p. 140 -145 2. Review questions p. 145

LO: Identify and describe earthquake-proof design features. SLE: Work collaboratively. Design and build an earthquake-proof building. Materials: 100 3 x 5 cards, 1 m masking tape, 10 straws. Rules: 1. You may only use the materials provided. 2. The building must be at least 50 cm tall and 20 cm wide. 3. The building must be free-standing. 4. The building must have 4 or more earthquake design features. 5. It must be able to withstand shaking for 30 seconds.

LO: Identify and describe earthquake-resistant design features SLE: Meet or exceed NGSS Checkpoint Quiz on Earthquake Design Features: Describe how each one of these features helps buildings survive an earthquake: 1. Mass damper: 2. Base isolator: 3. Cross beams: 4. Shear wall: 5. Underground pilings:

Volcanoes: A volcano is a crack or weak point in the earth’s crust through which magma comes near or onto the surface. (Once magma reaches the surface, it’s called lava. ) Magma: below ground Lava: above ground

Types of volcanic eruptions: Explosive: Non-explosive:

Structure of a volcano:

Products of Volcanic Eruptions: • Lava: the thickness of lava is determined by the amount of the mineral silica- the more silica, the thicker the lava. • Volcanic ash: dust and small bits of rock from explosive eruptions • Bombs: large rocks • Lapilli: small rocks • Gas: mostly CO 2, but also toxic gases • Pyroclastic flow: an avalanche of hot gas, ash and dust that flows down the side of the volcano at very high speeds.

Homework: LO: Describe causes and effects of volcanic eruptions SLE: Meet or exceed NGSS 1. Read p. 156 -161 (notebook) 2. Review questions p. 161 (loose leaf)

LO: Model effects of pressure on volcanic eruptions. SLE: Work Collaboratively Problem: What effect does increased pressure have on the force of volcanic eruptions? Hypothesis: Procedure: 1. Place 100 ml of vinegar in the bottom of a flask with a wider opening. 2. Add 2 -3 tsp of baking soda, and observe what happens. 3. Repeat steps 1 -2 with a flask with a narrow opening 4. Compare observations. Data: Using words or pictures, describe what happens with each “volcano. ” (qualitative data; record observations in words. Diagrams are OK. ) Conclusion:

Types of Volcanic Landforms: A volcanic landform is a feature of the earth’s surface that is created by volcanic eruptions. These include: • Shield volcanoes • Cinder cone volcanoes • Composite volcanoes • Lava plateaus • Calderas

Shield Volcanoes: Shield volcanoes are created by many layers of non-explosive (lava-only) eruptions. They have very gentle slopes, and can even be flat, but some of them are enormous. (The tallest mountain on earth is a shield volcano. )

Cinder Cone Volcanoes: Cinder cone volcanoes result from small to medium –sized explosive eruptions, and are made almost entirely of ash and dust (pyroclastic material). They tend to be small, but have very steep sides full of loose material.

Composite Volcanoes: Composite volcanoes are formed by alternating explosive and non-explosive eruptions. Inside, they have alternating layers of ash and lava. They are often dormant for thousands of years, but can also produce extremely large, destructive explosive eruptions. (All four of WA’s volcanoes are composite volcanoes. )

Lava Plateaus: Lava plateaus are formed when thin lava flows out from one or more long cracks in an area. Over many thousands or millions of years, many layers of lava form a high flat area (plateau). Some lava plateaus are gigantic: the Columbia Plateau in WA is a lava plateau.

Caldera: Sometimes, explosive eruptions are so large and violent that the entire magma chamber beneath a volcano empties out all at once. With nothing below to support the weight of an entire mountain, it collapses in on itself and forms a gigantic hole in the ground called a caldera.

LO: Identify and describe volcanic landforms SLE: Meet or exceed NGSS Volcanic Landforms Diagrams: Create a diagram that describes all 5 of the volcanic landforms we’ve discussed. For each landform, include: 1. A color diagram of the landform; 2. A caption that describes what kind of eruptions it has; 3. An example –name and location- of that type of landform (example: Columbia Plateau, Washington State, USA). Use a laptop to look up the names and locations of specific volcanic landforms.

Homework: LO: Identify and describe volcanic landforms. SLE: Articulate ideas clearly and effectively. Write a 7 -sentence (more is OK) paragraph that describes each major type of volcanic landform. Include a description of how each one is formed and what it looks like. Or: Write a 7 sentence paragraph that describes the dangers posed by volcanoes, and what we can do about these dangers.

Causes of Volcanic Eruptions: Volcanic eruptions are caused by the movement of tectonic plates at divergent and convergent plate boundaries: 1. At Convergent plate boundaries, rock is affected by friction between the plates, which causes the rock to get so hot it melts. The magma then reaches the surface via convection pressures through weak points in the rock.

The pressure placed on rocks affects when and where magma will form. Rock that is under a lot of pressure will not melt even if it is very hot. When pressure is released, it becomes less dense and turns into a liquid.

2. At divergent plate boundaries, volcanic eruptions usually occur because of lower pressure instead of higher temperatures, since temperature in the upper mantle is pretty constant. When plates move apart, the pressure decreases, the rock turns into a liquid, and magma floats to the surface.

Hot Spots: Sometimes (not often) volcanoes form in the middle of plates. Scientists believe this happens because bubbles of liquid rock (magma plumes) float to the surface through cracks or weak spots in the earth’s crust.

Classes of volcanic activity: 1. Active: volcanoes that have erupted recently, are erupting now, or are likely to erupt in the near future. 2. Dormant: Have erupted in the distant past, and are likely to erupt in the future, but not soon. 3. Extinct: Have not erupted for a long time and will not erupt again.

How volcanic eruptions are predicted: 1. Measuring small earthquakes near a volcano: if a lot of small earthquakes, caused by magma moving through the crust, are detected, it’s likely that an eruption will occur. 2. Measuring slope and temperature: if the surface on the slope of a volcano begins to bulge or shift, or if the temperature near the crater increases, the chances of an eruption are greater.

Homework: LO: Describe how volcanic eruptions occur. SLE: Meet or exceed NGSS 1. Read p. 166 -171 2. Respond to the review questions on p. 171

LO: Describe volcanic landforms. SLE: Meet or exceed NGSS Checkpoint quiz on volcanic landforms: 1. Describe how calderas are formed. 2. Draw a diagram of the inside of a composite volcano. 3. Which volcanic landform is completely flat and has only non-explosive eruptions? 4. Which volcanic landform only has explosive eruptions? 5. What type of volcanic landform is Mt. Rainier (Tahoma)?

LO: Describe how rocks are classified. SLE: Work collaboratively Introduction to Rocks: 1. Have a member of your table group select 9 rocks from my “collection. ” 2. With your group members, place the rocks in three groups based on a selection criterion chosen by you. (Color, roughness, beauty, etc. ) 3. Describe your selection to me and your class. 4. Repeat steps 2 -3 using a different selection criterion

Rocks: A rock is a naturally occurring mixture of two or more minerals. They can be formed through the cooling of magma or lava, under intense heat or pressure, through the process of erosion/deposition, or the activity of living things.

The rock cycle:

How rocks are classified: Scientists classify rocks according to their: 1. Composition: the minerals they’re made of. 2. Texture: the size, shape, and position of the grains that the rock is made of. 3. How they were formed (this is the most general way to classify rocks).

Homework: LO: Describe how rocks are classified. SLE: Meet or exceed NGSS 1. Read p. 28 -34 2. Review questions p. 35

Main Types of Rocks: Igneous: Rock that is formed from cooling magma or lava. Intrusive igneous rock forms from cooling magma below the earth’s surface. Because it cools very slowly, it has coarse-grained texture and large, irregular crystals. Extrusive igneous rock is formed from lava above the surface. It cools quickly, so it has small crystals or no crystals. Its texture depends on its mineral composition.

Sedimentary rock: Sedimentary rock is formed from sedimenteroded bits of clay, dust, mud or small pebbles that are pressed together into new rock at or near the surface. A key feature of sedimentary rock is that it forms in strata, or layers deposited on top of one another.

Types of sedimentary rock: Clastic sedimentary rock: when rock or mineral fragments are cemented together. Chemical sedimentary rock: When minerals in rock crystallize out of a solution (such as sea water) to form rock. Organic sedimentary rock: formed from the remains of dead organisms.

Metamorphic rock: Metamorphic rock is rock that has been transformed by heat and/or pressure deep within the earth’s crust. Types of metamorphic rock: Foliated: Crystals or grains are arranged in orderly, regular bands. Nonfoliated: Crystals or grains are randomly arranged.

Homework: LO: Describe three main classes of rock. SLE: Meet or exceed academic standards. 1. Read p. 36 -49. 2. Review questions p. 49