1-24-18 Evidence of Seafloor Spreading

Do Now: Read the following and answer the questions in your Science Notebook. When this Icelandic geyser erupts, watch out! The column of water and steam is extremely hot! Iceland is a volcanic island. Although the surface of Iceland can be quite cool, the rocks deep below are hot. Steam collects in spaces between the rocks and below a column of water. When the pressure rises high enough, the steam and water rush out of the geyser. What do geysers indicate about the temperature of Earth’s interior? Do you think a geyser could form under the ocean floor? If you could crack open Earth like an egg, what would you expect to find inside?

Do Now: Read the following and answer the questions in your Science Notebook. What do geysers indicate about the temperature of Earth’s interior? A: Geysers indicate that Earth’s interior is very hot. Do you think a geyser could form under the ocean floor? A: Structures on the ocean floor called “black smokers” act like the geysers observed on land. Black smokers release water that was heated deep under the ocean’s surface. If you could crack open Earth like an egg, what would you expect to find inside? A: Earth’s interior contains magma, which is hot, molten rock.

Homework Work on Science Fair Project. See the “News” page on the class website, www.scascience7.weebly.com/news, for all of the rubrics and instructions for the different parts of your Science Fair project. Science Fair is this Thursday, 1/25!

Oral Presentation Tips ✓ Refrain from reading directly from your presentation. ✓ Stand off to the side of your project so it is visible. ✓ Appearance is important. Wear your CSUSA uniforms proudly. ✓ Stand up straight and tall. Introduce yourself confidently. Look directly at your judges or into the camera and speak in a clear, friendly tone. ✓ Follow the criteria on the CSUSA Science Fair Rubric to guide your presentation. ✓ Be confident! Be proud of yourself. You have worked hard on this project.

Sample Presentation Introduce your science fair project and provide a brief description about the topic. Describe the data collection and how you organized the information. Remember to refer to units of measurement. Explain why you chose your project. For example, “The reason I chose this particular project is because…”Explain why: interesting, fun, challenging, beneficial, applicable, etc. Describe the results. “After following all of the steps in the procedure, the results I found were…” Explain the outcome. What happened? Do not omit any details in the results that could be useful in the conclusion. State your hypothesis along with your predicted outcome. “My hypothesis was…” Describe the conclusion. “From the results I came to the conclusion…” What did you learn? Was your hypothesis accurate? Your hypothesis may be incorrect; therefore you can discuss what you learned. Describe the materials used in your experiment. List materials and state how they were relevant to the experiment, as well as any safety precautions you had to take. Did you enjoy the process? Is there anything else you can draw from your conclusion? Describe the procedure you followed. List the steps IN ORDER and thoroughly explain each. Describe the resources used to research information regarding your topic. Discuss the variables you included in your experiment. Thank the judges for their time.

Seafloor Spreading Lesson Objective: Students should be able to explain seafloor spreading and the evidence used to support seafloor spreading. Standards: SC.7.E.6.2, SC.7.N.1.3, SC.7.N.1.5, SC.7.N.1.6, SC.7.N.2.1

Student Work: Practice – 10 min With a shoulder partner, complete the Key Concept Builder worksheet.

Student Work: Practice It becomes lava and cools to form rock. pillow lavas at the mid-ocean ridge It moves away from the mid-ocean ridge. Magma that rises through cracks on the seafloor erupts and becomes lava. The lava cools rapidly in the ocean, forming rock structures. This new rock is located at the mid-ocean ridges. Older rock is carried away as the seafloor spreads.

Essential Questions What is seafloor spreading? What evidence is used to support seafloor spreading?

Evidence of Seafloor Spreading The first evidence used to support seafloor spreading was discovered in rocks on the seafloor. Scientists studied the magnetic signature of minerals in these rocks. Earth’s magnetic field today is described as having normal polarity—a state in which magnetized objects, such as compass needles, will orient themselves to point north. Polaridad normal: ocurre cuando los objetos magnetizados, tales como las agujas de la brujula, se orientan a si mismas para apuntar al norte.

Evidence of Seafloor Spreading Sometimes a magnetic reversal: an event that causes a magnetic field to reverse direction, occurs and the magnetic field reverses direction. Inversion magnetica: evento que causa que un campo magnetico invierta su direccion The opposite of normal polarity is reversed polarity: a state in which magnetized objects reverse direction and orient themselves to point south. Polaridad inversa: ocurre cuando los objetos magnetizados invierten la direccion y se orientan a si mismos para apuntar al sur.

Evidence of Seafloor Spreading Volcanic rock on the seafloor contains iron-rich minerals that are magnetic. Magnetic minerals in cooling lava from the mid-ocean ridge record the direction of Earth’s magnetic field. Scientists have discovered parallel patterns in the magnetic signature of rocks on either side of a mid-ocean ridge.

Evidence of Seafloor Spreading Each pair of stripes has a similar composition, age, and magnetic character. The pairs of magnetic stripes confirm that the ocean crust formed at mid-ocean ridges is carried away from the center of the ridges in opposite directions.

Evidence of Seafloor Spreading Other measurements made on the seafloor confirm seafloor spreading. Measuring the amount of thermal energy leaving the Earth shows that more thermal energy leaves Earth near mid-ocean ridges than is released from beneath the abyssal plains. Magma is contributing to the high thermal energy flow readings near the center of a mid-ocean ridge.

Evidence of Seafloor Spreading Sediment collected from the seafloor can be dated to show that the sediment closest to the mid-ocean ridge is younger than the sediment farther away from the ridge. This is done by measuring the amount of “parent” radioactive elements and non- radioactive “daughter” elements. The age of the rock in years can be found by measuring the rate at which a parent element decays and then measuring the ratio of parent element to daughter element in the rock

A magnetic reversal occurs when Earth’s magnetic field changes direction.

Lesson 2 – LR1 As the seafloor continues to spread apart, the older oceanic crust moves in which direction with respect to the mid-ocean ridge? A. toward it B. above it C. away from it D. under it

Lesson 2 – LR2 Today’s magnetic field is described as having which of these? A. reversed polarity B. normal polarity C. magnetic reversal D. no polarity

Lesson 2 – LR3 In which state do magnetized objects reverse themselves to point south? A. reversed polarity B. normal polarity C. seafloor spreading D. magnetic polarity