ASTR 1514 1st Edition Lecture 14Tectonism Chapter 6.3Tectonism – The deformation of Earth’s crust.- The Lithosphere is broken into plates around the Earth they are drifting- Continental Drift and plate tectonics describe the movement of those plates- Crustal plates move due to convection, the rising and falling of hot/cold material. - Continental plates are made of lower density rock so they float on top and are dragged around.- Earth has seven major plates and six smaller ones that are all continually moving. - Plates can separate, collide or move parallel to each-other. There are several types of motion/features that are due to tectonic plates1. Sea-Floor Spreading- Two plates separate and new lithosphere is created at the boundary of their separation. - Sea-floor spreading gives us direct evidence for change in Earth’s magnetic field direction. 2. Plate Collisions (Convergence)- Continental plates float on the mantle where they collide and form mountains. - Example: Indian plate colliding or converging with the Eurasian plate to form the Himalaya Mountains. 3. Subduction- Also a type of converging or colliding plate boundary. - Occurs when dense sear-floor crust sinks under less dense continental plates. - Subducting plate bends in a “plastic” manner due to water content. - Subducting plate sinks due to thickness and weight, weight pulls it down.- Ex: Coast of Oregon/Washington. 4. Continental Plates pull apart (Diverge)- When Continental plates pull apart a rift valley may be formed- Ex: Great African Rift Valley. And Iceland Rift Valleys. 5. Plates sliding past each other (Transform Boundary)- Plates may slide sideways with respect to one another- Ex: San Andreas Fault in California. 6. Hot Spots- Hot spots mark a plume of hot mantle - The pacific plate moves over hot spots creating a string of islands. - Ex: Hawaiian Islands. Earthquakes commonly occur along plate boundaries, most often occur along converging or colliding plate boundaries. Tectonics onOther Terrestrial Planets- Only Earth has its crust broken up into plates- All terrestrial planets have seen some form of disruption. Ex: Mercury’s surface shrank after it cooled, leaving cliffs.- Mars has experienced extensive tectonism, it is home to the Valles Marineris (Giant Rift Valley) that is four times deeper than Earth’s Grand Canyon. - Venus may have different forms of tectonism, with melting and overturning of the crust and some hot spots. Volcanoes Chapter 6.4- Volcanoes form (primarily) at hot spots and plate boundaries.- Friction raises the temperature of the rock along plate boundaries to its melting point. - Two different kinds of Volcanoes1. Shield Volcanoes Formed from very fluid like lava Low water content in the rock Formed from low – viscosity (Runny, liquidy) lava from basaltic rock. 2. Composite Volcanoes  Formed from pasty viscous (thick and slow like molasses) lava High water content in rocks Lithosphere created at mid-ocean ridges gains thickness and water due to sediment build up and dead animals When the heavy rock sinks below the continental plate it is heated due to friction producing composite volcanoes. Common along subduction zones Explosive Volcanic Activity.The Moon- Does NOT have volcanoes- Lava flows smoothed out parts of its surface, could’ve been impacts cracking surface.Mercury- Also has smooth surfaces from past volcanism’- A few inactive volcanoes have been identified on Mercury.Mars- Volcanoes on Mars are the largest mountains in the Solar System- Shield Volcanoes- Olympus Mons – Highest Volcano in the entire Solar System- No currently active volcanoes on Mars- Mars is a small planet that possibly cooled too much. Venus - Has most of the volcanoes of the terrestrial planets- All of Venus’s volcanoes are shield volcanoes, so no plate tectonics- Surface too hot and dry so plates dried out - Few craters: Surface of Venus is about half a billion years old, could have been a global crust break up and turnover. - Venus’s volcanoes are mostly inactive- Monitoring of sulfur dioxide in Venus’s atmosphere has shown changes over past 30 years indicating a little volcanic activity. - Baltis Vallis – Longest lava flow in solar system. Erosion Chapter 6.5- Erosion is the wearing a way of a planet’s surface by mechanical action. (Running water, Wind, etc.)- Wind modifies the surfaces of Venus and Mars- Landslides and radiation from the Sun also change the surface. - On Earth, the only planet with liquid water today, wind and water strongly erode the surface.- Water modified the surface of Mars in the past and it exists as ice today. - Water ice exists on Mars, the moon, and possibly Mercury. Geology of Oklahoma- Much of Oklahoma is Sedimentary rock- Used to be covered by a shallow sea that rose and fell over the eons- Metamorphic Rocks in Oklahoma: Ouachita Mountains/Arbuckle Mountains.- Igneous Rocks in Oklahoma: Wichita Mountains- Wichita Mountains formed from lava flowing into a rift valley. It was then buried under layers of shale. Uplifted due to the collision between North America and South America. - New Madrid Fault is a failed rift zone, an Earth-quake in 1811-1812 caused Mississippi River to run backwards.- Magnitude 6 Earth-quake expected to occur every 100