Science-Q1 Earth and Space (Earth Parts)

Earth and Space

1. Q1-EARTH AND SPACE The Solid Part of the Earth

2. OBJECTIVE: 1. Describe the Earth’s lithosphere 2. Differentiate oceanic and continental crust 3. Infer that the Earth’s lithosphere is divided into plates 4. Identify the major lithospheric plates

3. Recall: Identify the sphere of the earth being described in the following: __________1.The nitrogen cycle. __________2. Waves in the ocean. __________3. The rocky surface of the earth. __________4. The animals that live in land and water

4. VIDEO PRESENTATION Introduction to Oceanic and Continental Crust ► https://www.youtube.com/watch?v=ZwV-OfUGxNQ&authuser=0 Oceanic versus Continental Crust ► https://www.youtube.com/watch?v=9u4NhAXAuj8&authuser=0 The Lithosphere ► https://www.youtube.com/watch?v=et0DcFhX8Ig&authuser=0

5. FACTS ABOUT EARTH’S LITHOSPHERE One of the earth’s sphere is Lithosphere. According to Wikipedia, lithosphere (Ancient Greek: λίθος [lithos] for "rocky", and σφαίρα [sphaira] for "sphere") is the rigid, outermost shell of a terrestrial -type planet, or natural satellite, that is defined by its rigid mechanical properties. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater. The outermost shell of a rocky planet, the crust, is defined on the basis of its chemistry and mineralogy. The layer under the lithosphere is known as the asthenosphere. According to Merriam-Webster, lithosphere is the outer part of the solid earth composed of rock essentially like that exposed at the surface, consisting of the crust and outermost layer of the mantle, and usually considered to be about 60 miles (100 kilometers) in thickness.

6. The lithosphere is the outer solid part of the earth, including the crust and uppermost mantle. The lithosphere is about 100 km thick, although its thickness is age dependent (older lithosphere is thicker). Lithosphere below the crust is brittle enough at some locations to produce earthquakes by faulting, such as within a subducted oceanic plate.

7. Differences Between Oceanic and Continental Plates

8. Differences in Composition. Oceanic plates are mafic in nature, composed of basalt rock and its coarse-grained equivalent, gabbro, both rich in iron, magnesium and calcium. In contrast, continental plates are felsic in nature, dominated by granitic rock with its abundant silica, aluminum, sodium and potassium. Metamorphic and sedimentary rocks also help build continental crust, much more varied geologically than its oceanic counterpart. Differences in Density . Because of their heavy ferromagnesian elements, oceanic plates are much denser than continental plates. The average density of ocean plates is approximately 200 pounds per cubic foot, while continental crust ranges between about 162 and and 172 pounds per cubic foot. This difference in relative density causes oceanic plates to subduct beneath the more buoyant continental plates. This also allows the denser oceanic plates to sink further into the fluid asthenosphere, causing them to lie below sea level. In contrast, the more buoyant continental plates float higher, resulting in dry land.

9. Differences in Range and Thickness. Oceanic plates cover approximately 71 percent of Earth’s surface, while continental plates cover 29 percent. While oceanic plates cover far more area, they are much thinner than continental crust. Despite their greater density, oceanic plates average only about four or five miles in thickness, compared to an average of 25 miles for continental plates; under major mountain belts, the continental crust can reach nearly 50 miles thick. The combination of their respective area and average thickness means that there is actually twice as much continental rock as oceanic rock. Differences in Formative Process. Oceanic plates are formed by divergent plate boundaries. These zones, located along mid- ocean ridges, represent areas where upwelling magma creates new oceanic crust. As lava flows from these volcanic ridges, it quickly cools, forming extrusive igneous rock. Continental plates, meanwhile, are formed primarily by convergent plate boundaries. These zones represent areas where oceanic plates collide with and plunge underneath continental plates – a process called subduction. As oceanic plates subduct, they melt to form magma. This magma cools over millions of years, producing intrusive igneous rock and new continental crust.

10. Differences in Age. Oceanic and continental plates differ radically in age because of tectonic processes. Divergent plate boundaries continually renew oceanic plates while the subduction zones of convergent boundaries continually recycle them. As a result, the oldest oceanic rocks are less than 200 million years old. In contrast, continental plates take a long time to form but are rarely destroyed. Much of the continental crust exceeds 1 billion years in age, and its oldest rocks may be as old as 4 billion years.

11. REMEMBER: ●LITHOSPHERE IS THE SOLID PART OF THE EARTH WHERE EARTHQUAKES OCCUR. IT IS WHERE THE PEOPLE LIVE. ●LITHOSPHERE IS THE SOLID, OUTER PART OF THE EARTH, INCLUDING THE BRITTLE UPPER PORTION OF THE MANTLE AND THE CRUST. ●THERE ARE TWO TYPES OF CRUST; CONTINENTAL AND OCEANIC. ●LITHOSPHERE IS DIVIDED INTO MAJOR AND MINOR LITHOSPHERIC PLATES.

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