SCIED 53: EARTH SCIENCE Introduction to Geology PDF

SCIED 53: EARTH SCIENCE INTRODUCTION LA TIERRA TO EARTH SCIENCE GEOLOGY: THE SCIENCE OF THE EARTH WHAT IS GEOLOGY? WHAT IS GEOLOGY? -a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes b...

SCIED 53: EARTH SCIENCE INTRODUCTION LA TIERRA TO EARTH SCIENCE GEOLOGY: THE SCIENCE OF THE EARTH WHAT IS GEOLOGY? WHAT IS GEOLOGY? -a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. WHAT IS GEOLOGY? Geology as a formal science started on the 18th century but it has deeper roots that stretch back further. In the 18th century, the field gained more structure and recognition through the work of several key figures. the word geology comes from the greek words “geo” means earth and “logos” which means knowledge.  2 Broad Areas of GEOLOGY: PHYSICAL HISTORICAL GEOLOGY GEOLOGY  PHYSICAL GEOLOGY -scientific discipline that is concerned with all aspects of the Earth's structure, composition, physical properties, constituent rocks and minerals, and surficial features.  HISTORICAL GEOLOGY -examines the vastness of geologic time, measured in billions of years, and investigates changes in the Earth, gradual and sudden, over this deep time. THE DEVELOPMENT OF GEOLOGY Aristotle 384-322 BC Most influencial greek Philosopher Deduced that the positions of land and sea had changed and thought these changes occurred over long periods of time. James Ussher Ussher constructed a chronology of human and Earth history in which he calculated that Earth was only a few thousand years old, having been created in 4004 b.c.e. Georges Cuvier A French Paleontologist who promotes the idea of catastrophism. Cuvier noticed that fossils of organisms seemed to cease immediately above some geological epochs and strata. Georges Cuvier led him to believe that Earth's history of life comprised long periods of stability that were interrupted abruptly by catastrophe, some of which Cuvier imagined as recurring. James Hutton A Scottish physician and gentleman farmer, who published Theory of the Earth in 1795. put forth a fundamental principle that is a pillar of geology today: Uniformitarianism. Charles Lyell a 19th-century British geologist, is renowned for his pivotal role in shaping modern geological thought. His work built upon and expanded the ideas introduced by James Hutton, and his contributions significantly influenced the field of geology.  CATASTROPHISM VS. UNIFORMITARIANISM CATASTROPHISM is a previous geological paradigm and theory that explains Earth's current landscape and shape as forming out of abrupt, violent, short-lived, and maybe even global events resulting in mass extinction and the changing landscape. UNIFORMITARIANISM the idea that Earth has always changed in uniform ways and that the present is the key to the past. The earth sculpting processes alluded to above are the processes of erosion, deposition, compaction and uplift. Although these processes are constant, they occur at extremely slow rates. UNIVERSE BEGINS Our scenario begins about 13.7 billion years ago with the Big Bang, an incomprehensibly large explosion that sent all matter of the universe flying outward at incredible speeds. It was in one of these galaxies, the Milky Way, that our solar system and planet Earth took form. NEBULAR THEORY is a dynamic combination of interconnected components, including the spheres of the earth, this components interact to form an integrated whole. aims to study Earth as a system composed of numerous interacting parts, or subsystems. The hydrosphere is a dynamic mass of water that is continually on the move, evaporating from the oceans to the atmosphere, precipitating to the land, and running back to the ocean again. Earth is surrounded by a life-giving gaseous envelope called the atmosphere. This is a thin blanket of air is an integral part of the planet. It not only provides the air we breathe but also protects us from the Sun’s intense heat and dangerous ultraviolet radiation. The biosphere includes all life on Earth. Plants and animals depend on the physical environment for the basics of life. However, organisms do not just respond to their physical environment. Through countless interactions, life-forms help maintain and alter the physical environment. Beneath the atmosphere and the oceans is the solid Earth, or geosphere. The geosphere extends from the surface to the center of the planet, a depth of nearly 6400 kilometers (nearly 4000 miles), making it by far the largest of Earth’s four spheres. The crust, Earth’s relatively thin, rocky outer skin, is of two different types— continental crust and oceanic crust. Both share the word crust, but the similarity ends there. More than 82 percent of Earth’s volume is contained in the mantle, a solid, rocky shell that extends to a depth of about 2900 kilometers (1800 miles). The Upper Mantle The upper mantle extends from the crust–mantle boundary down to a depth of about 660 kilometers (410 miles). The upper mantle can be divided into three different parts. The top portion of the upper mantle is part of the stronger lithosphere, and beneath that is the weaker asthenosphere. The bottom part of the upper mantle is called the transition zone  Beneath this stiff layer to a The Lithosphere ("rock depth of about 410 km lies a sphere") consist of the entire soft, comparatively weak crust plus the upper most layer known as the mantle and forms Earth's asthenosphere. relatively cool, rigid outer shell. From about 410 km to about 600 km in depth is the part of the upper mantle called the transition zone. The Lower Mantle From a depth of 660 kilometers (410 miles) to the top of the core, at a depth of 2900 kilometers (1800 miles), is the lower mantle. The core is composed of an iron–nickel alloy with minor amounts of oxygen, silicon, and sulfur—elements that readily form compounds The outer core is a liquid layer with iron. 2250 kilometers (1395 miles) thick. The inner core is a solid layer sphere that has a radius of 1221 kilometers (757 miles). ROCKS AND THE ROCK CYCLE  ROCKS Rocks are the most common and abundant material on Earth. It is naturally occurring solid substances composed of minerals or organic materials. Rocks can vary in terms of their composition and properties.  HAVE YOU EVER WONDERED HOW ROCKS TRANSFORM AND CHANGE OVER TIME?  ROCK CYCLE is a series of processes that helps us understand the origin of igneous, sedimentary, and metamorphic rocks and to see that each type is linked to the others by processes that act upon and within the planet.  IGNEOUS ROCKS Magma is molten rock formed deep beneath Earth's surface. When magma cools and solidifies, it undergoes crystallization. This process results in the formation of igneous rocks, either intrusive (beneath the surface) or extrusive (at the surface).  SEDIMENTARY Exposed igneous rocks undergo weathering by atmospheric, hydrospheric, and biospheric forces. Weathering breaks rocks into particles and dissolved substances, known as sediment. Sediment is transported by gravity and erosional agents (water, glaciers, wind, waves). Deposition occurs in oceans, river floodplains, deserts, swamps, and sand dunes.  SEDIMENTARY ROCKS Sediments are converted into sedimentary rock through lithification. Lithification occurs by compaction under the weight of overlying layers. Cementation happens as groundwater fills sediment pores with mineral matter. METAMORPHIC ROCKS Buried sedimentary rock exposed to high pressure or intense heat transforms into metamorphic rock. Metamorphic rock may further melt under extreme conditions, forming magma. THE GREAT DEBATE  ALFRED LOTHAR WEGENER Wegener was a German meteorologist, geophysicist and polar researcher. In 1915 he published ‘The Origin of Continents andOceans’, which outlined his theory of Continental Drift.  TWO ASPECTS OF WEGENER’S CONTINENTAL DRIFT HYPOTHESIS THAT WERE OBJECTIONAL GRAVITATIONAL FORCE OF SUN AND MOON Wegener suggested that the gravitational forces of the Moon and Sun, responsible for Earth's tides, could also move the continents. This idea was rejected because physicist Harold Jeffreys argued that such forces, if strong enough to move continents, would have also stopped Earth's rotation, which clearly has not occurred.  CONTINENTS BREAKING THROUGH OCEANIC CRUST Wegener proposed that the continents moved by breaking through the oceanic crust, much like icebreakers cut through ice. This idea was objectionable because it lacked supporting evidence and did not align with observations. The oceanic crust was not weak enough to allow such movement without causing significant deformation, which was not observed. Wegener’s ideas were ridiculed, particularly in North America, but some geologists found them plausible and continued to explore the concept. Although most of the scientific community rejected his theory, Wegener's work laid the foundation for the modern understanding of plate tectonics. PLate tECtonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the molten rocky layer above the core. plates Plates 'float' on the molten rock magma. As the core of the Earth heats up the materials inside, the molten magma also gets heated up. The heat causes convection currents, a movement of rising and sinking caused by heat, inside the molten magma. Forces that drives plate motion slab pull ridge push convection plate boundaries The location where two plates meet is called a plate boundary. Plate boundaries are where geological events occur, such as earthquakes and the creation of topographic features such as mountains, volcanoes, mid-ocean ridges, and oceanic trenches.  Divergent Boundary -occur along spreading centers where plates are moving apart and new crust is created by magma pushing up from the mantle. Picture two giant conveyor belts, facing each other but slowly moving in opposite directions as they transport newly formed crust away from the ridge crest. The Mid-Atlantic Ridge is an example of divergent boundaries where new plate material is made. This is referred to as sea-floor spreading. As the plates drift apart, molten rock from the mantle rises to fill the gap, cools and solidifies to form new oceanic crust in the form of a ridge. The ridges are a continuous chain of submarine mountains. Convergent Boundary occur when two plates move towards each other (converge). While the motion of the plates is the same, the resulting landforms can be very different depending on the type of plates involved. g also called subduction zones because they are sites where lithosphere is descending (being subducted) into the mantle. Subduction occurs because the density of the descending lithospheric plate is greater than the density of the underlying asthenosphere. Oceanic-continental convergent boundary: When a continental and an oceanic plate converge, the oceanic plate is always subducted. This is because oceanic crust is much denser than continental crust. A trench forms on the ocean floor at the subduction zone, and a volcanic arc (a volcanic mountain range) forms on the continental plate parallel to the trench. Deep earthquakes can form in the subduction zone.  Ocean to Ocean Collision When two oceanic plate collide, it can result in the formation of volcanoes, too. One oceanic plate sink beneath the other, and over millions of years, the erupted lava and volcanic debris pile up on the ocean floor. Finally, a volcano rises above sea level to form an island volcano. Such volcanoes are typically strung out in chains called island arcs. This is how the Aleutian Islands have formed and why they experience numerous strong earthquakes.  Continent-Continent Collision: were created when two continental plates met head- on,and neither was subducted. Continental rocks are relatively light and, like two colliding icebergs, resist downward motion. Instead, the crust buckled and was pushed upward and sideways India collided into Asia 50 million years ago, causing the Eurasian Plate to crumple up and override the Indian Plate. After the collision, the slow continuous convergence of the two plates over millions of years pushed up the Himalayas and the Tibetan Plateau to their present heights. The Himalayas, towering as high as 8,854 m above sea level, are the highest continental mountains in the world. Transform plate Boundary Two plates moving horizontally past each other form a transform fault. In this process, the crust is fractured and deformed, but it is not destroyed (as it is in convergent boundaries) or created (as it is in divergent boundaries). This action often causes shallow earthquakes. Transform boundaries are very common around mid-ocean ridges, but also occur in continental crust. The San Andreas Fault Stretches about 1,300 km long and in some places tens of kilometers wide. Slices through two thirds of the length of California. The Pacific Plate has been grinding horizontally past the North American Plate for 10 million years, at an average rate of about 5 cm/yr. How Is Plate Motion Measured? GPS satellites can be used to accurately measure the motion of special receivers to within a few millimeters. These “real-time” data support the inferences made from seafloor observations. Plates move at about the same rate human fingernails grow: an average of about 5 centimeters (2 inches) per year. EVIDENCES OF THE PLATE TICTONIC THEORY  Alfred lothar Wegener (1) the shape of the continents, (2) continental fossil organisms that matched across oceans, (3) matching rock types and modern mountain belts, and (4) sedimentary rocks that recorded ancient climates, including glaciers on the southern portion of Pangaea. Evidence: The Continental Jigsaw Puzzle The coast lines of some continents appear to fit together like a jigsaw puzzle. Scientists propose that about 300 million years ago. the continents were joined together into one single landmass (or supercontinent) called Pangaea. Over tens of millions of years. Pangaea began to break apart, moving the continents to their current locations. Two of the puzzle pieces The best fit of South America and Africa along the continental slope at a depth of 500 fathoms (about 900 meters )[3000 feet]). (Based on A. G. Smith, “Continental Drift,” in Understanding the Earth, edited by I. G. Gass, Artemis Press.) Evidence: Fossils Matching Across the Seas it was when he learned that identical fossil organisms had been discovered in rocks from both South America and Africa. A classic example is Mesosaurus, a small aquatic freshwater reptile whose fossil remains are limited to black shales of the Permian period (about 260 million years ago) in eastern South America and southwestern Africa. Evidence: Rock Types and Geologic Features If the continents were once together, the rocks found in a particular region on one continent should closely match in age and type those found in adjacent positions on the adjoining continent. Wegener found evidence of highly deformed igneous rocks in Brazil that closely resembled similar rocks in Africa.  Evidence: Ancient Climates Because Alfred Wegener was a student of world climates, he suspected that paleoclimatic (paleo = ancient, climatic = climate) data might also support the idea of mobile continents. His assertion was bolstered by evidence that a glacial period dating to the late Paleozic had been discovered in southern Africa, South America, Australia, and India. This meant that about 300 millon years ago, vast ice sheets covered extensive portions of the Southern Hemisphere as well as India. THANK YOU