SUN Hydrogen (74%), some helium (24%) Rocky inner planets Silicates with Iron/Nickel cores The giant Gas planets of the outer solar system Hydrogen, Helium, methane, water, ammonia
Where did the water for the oceans come from? From volcanoes: Ammonia (NH 3 ) Hydrogen (H 2 ) Carbon dioxide (CO 2 ) Methane (CH 4 ) Water vapor (H 2 O) Nitrogen (N 2 )
Hadean Oceans Characteristics Liquid Water existed at 4.4 Gyrs Ephemeral (periodically vaporized) Acidic (water + carbon dioxide = carbonic acid) Probably salty Stabilized by end of Hadean (about 3.8 Gyrs) Evidence Jack Hills Formation zircon crystals with water inclusions solar system evidence for heavy bombardment and models no limestones, atmospheric models acidic water (dissolves ions) first limestones & sedimentary rocks
What is different about the Earth? Tectonically Active: No or very few craters visible. The lithosphere (rocky outer crust) is moving. (Venus and some of the moons of Jupiter and Saturn may also be somehat active) Why is this? Dynamic Hydrosphere/Atmosphere: Clouds, winds, waves, currents, etc. (something similar on Jupiter and Mars, but different in magnitude and/or kind) Dynamic Biosphere: you can see life on the Earth in the reflected radiation and in the fact that there is Oxygen in the atmosphere.
MAIN IDEA 1 Planet Earth The major geologic features of Earth's surface are (1) the surface fluids (air and water), (2) the continents, and (3) the ocean basins. The characteristics of these features indicate that Earth is undergoing constant change. Earth is unique in the Solar System. SUPPORTING IDEAS 1. A comparison of Earth with other terrestrial planets provides an insight into the distinguishing characteristics of our planet and what makes it unique. 2. Earth's atmosphere is a thin shell surrounding the planet and is in constant motion. It is unique in the Solar System in that it is composed of 78% nitrogen and 21% oxygen. 3. The hydrosphere is another feature that makes Earth unique. It moves from the ocean to the atmosphere and over the surface in a great cycle. 4. The biosphere exists because of water. Although it is relatively small compared with other major layers of Earth, the biosphere has been a major geologic force operating at the surface.
5. Continents and ocean basins are the principal surface features of Earth. 6. The continents consist of three major components: (a) shields, (b) stable platforms, and (c) belts of folded mountains. All these components show the mobility of the crust. 7. The ocean floor contains several major structural and topographic divisions: (a) the oceanic ridge (b) the abyssal floor, (c) seamounts, (d) trenches, and (e) continental margins. 8. Earth is a differentiated planet, with its materials segregated and concentrated into layers according to density. The internal layers based on composition are (a) crust, (b) mantle, and (c) core. The major internal layers based on physical properties are (a)lithosphere, (b) asthenosphere, (c) mesosphere, (d) outer core, and (e) inner core. Material within these units is in motion, making Earth a changing, dynamic planet.
The Hydrosphere Total mass of water on or near the Earth s surface Covers 71% of Earth s surface ~98% in oceans 2% in glaciers, groundwater, lakes and streams (fresh water) The presence of water moderates climates and shapes the Earth s surface
Compositional Layers Crust Continental crust Thicker than oceanic crust - up to 75 km Less dense - 2.7 g/cm 3 Strongly deformed Much older - may be billions of years old
Compositional Layers Crust Oceanic crust Thinner than continental crust - about 8 km More dense - 3.0 g/cm 3 Comparatively undeformed Much younger - < 200 million years old Composed of basalt
Crustal Properties Crust Density Composition Thickness Age continental ~2.8 g/cm 3 Felsic Thick: 20-70 km Old: up to 4 Byrs oceanic ~3.2 g/cm 3 Mafic Thin: 2-10 km Young: <200 Mys
30_SeaFloor.swf
Ocean Basins
Key Ideas Earliest direct evidence for voyaging was from the Mediterranean. There may well have been intentional or unintentional ocean travel previous to that time. The origins of marine science lie in voyaging traveling on the ocean for a purpose, which varied form one culture and time to another. Technological advances made during voyaging and later marine exploration led to the rise of scientific oceanography. Earth s shape and circumference were accurately estimated around 230 B.C. at the Library of Alexandria, Egypt. The use of latitude and longitude for positioning and navigation also began there. Polynesian adventurers were the first to perfect methods of sustained, long-distance, open-ocean travel. Possibly as early as 900 BCE, but surely by 300 AD The first systematic voyages of oceanic exploration were undertaken by the Chinese in the fifteenth century.
Key Ideas Continued Christopher Columbus did not discover North America, and he did not sail around the world. Captain James Cook, Royal Navy, was perhaps the first ocean observer careful enough to be considered a marine scientist. The Challenger expedition was the first purely scientific voyage of oceanic exploration. Polar Studies greatly advanced marine science at the beginning of the twentieth century. Nearly all research is conducted not by individuals but by teams of specialists working in large, nationally funded oceanographic or military institutions. Satellites are increasingly important tools of oceanographic research.
A third century B.C. chart showing the system of latitude and longitude developed by Eratosthenes.
The Chinese Undertook Organized Voyages of Discovery Chinese navigators set out in the early 1400s to explore the Indian Ocean, Indonesia, Africa and the Atlantic. Their ships were laden with gifts designed to show China s wealth and degree of civilization! The Chinese invented: The central rudder Water-tight compartments Sails on multiple masts marine compass
Benjamin Franklin and the Gulf Stream
The British Challenger expedition of 1872-1876 was the first oceanic expedition dedicated to scientific research.
New Ships for New Tasks Ocean drilling (sediment and rock), water sampling (Temperature, Salinity, chemistry, etc), Echo sounders, side scan radar, submersibles, Remotely Operated Vehicles (ROVs) and now satellites in space (TOPEX, SeaWifs etc)
Blue = No deposition
What about changes in sea level? glacial/interglacial timescale Increase of ~120 meters
What about changes in sea level? Over Figure the last 5.13 century Increase of ~15 centimeters
Continental Margins Components: 1. Continental shelf = the shallow, submerged edge of the continent 2. Shelf break = the abrupt transition from continental shelf to the continental slope 3. Continental slope = the transition between the continental shelf and the deep-ocean floor 4. Continental rise = thick accumulations of sediment found at the base of the continental slope
Continental slope Continental rise
Deep Ocean Basins Major features: Mid-ocean ridges Fracture zones and transform faults Hydrothermal vents Shallow earthquakes Abyssal plains Abyssal hills Seamounts and guyots Oceanic trenches Volcanic arcs Deep earthquakes
Mid Ocean Ridge Spreading
Abyssal Plains Abyssal plains = broad flat areas of sediment-covered ocean floor found between the continental margins and the mid-ocean ridges Typically 4-6 km below sea level The flattest surface on Earth Sedimentation rates are very slow -- millimeters/1000 years! Mostly very fine clay, windblown dust, and shells of microscopic organisms Carbonate sediments are rare, as most of the plain is below the Carbonate Compensation Depth (CCD)
Continental Margins Components: 1. Continental shelf = the shallow, submerged edge of the continent 2. Shelf break = the abrupt transition from continental shelf to the continental slope 3. Continental slope = the transition between the continental shelf and the deep-ocean floor 4. Continental rise = thick accumulations of sediment found at the base of the continental slope
Continental slope Continental rise
Deep Ocean Basins Major features: Mid-ocean ridges Fracture zones and transform faults Hydrothermal vents Shallow earthquakes Abyssal plains Abyssal hills Seamounts and guyots Oceanic trenches Volcanic arcs Deep earthquakes
Abyssal Plains Abyssal plains = broad flat areas of sediment-covered ocean floor found between the continental margins and the mid-ocean ridges Typically 4-6 km below sea level The flattest surface on Earth Sedimentation rates are very slow -- millimeters/1000 years! Mostly very fine clay, windblown dust, and shells of microscopic organisms Carbonate sediments are rare, as most of the plain is below the Carbonate Compensation Depth (CCD)
Oceanic-Oceanic and Oceanic-Continental Subduction Zones
Passive Continental Margin