Ch. 1 Dynamic and Evolving Earth ESCI 102 Spring 2005

Lec. 1 Review/Summary Questions 1)What are the five subsystems of Earth? 2)Are there any more details known about early Earth? 3)If everything in the universe is moving away from us, why is it that we are not the center of the universe? 4)How has Earth’s core stayed hot for so long?

Earth’s Interior Layers Crust km thick –continental and oceanic Mantle –composed largely of peridotite –dark, dense igneous rock –rich in iron and magnesium Core –iron and a small amount of nickel

Earth’s Interior Layers Crust km thick –continental and oceanic Mantle –composed largely of peridotite –dark, dense igneous rock –rich in iron and magnesium Core –iron and a small amount of nickel Lithosphere –solid upper mantle and crust Asthenosphere –part of upper mantle –behaves plastically and slowly flows

Earth’s Interior Layers Lithosphere –solid upper mantle and crust Asthenosphere –part of upper mantle –behaves plastically and slowly flows –broken into plates that move over the asthenosphere

Earth’s Crust continental (20-90 km thick) –density 2.7 g/cm 3 –contains Si, Al oceanic (5-10 km thick) –density 3.0 g/cm 3 –composed of basalt

Plate Tectonic Theory Lithosphere is broken into individual pieces called plates Plates move over the asthenosphere –as a result of underlying convection cells

Modern Plate Map

Plate Tectonic Theory at plate boundaries –volcanic activity occurs –earthquakes occur movement at plate boundaries –plates diverge –plates converge –plates slide sideways past each other

Plate Tectonic Theory types of plate boundaries Transform Divergent Cont.-Cont. Convergent Cont.-Ocean Convergent Ocean-ocean Convergent

Plate Tectonic Theory influence on geological sciences: revolutionary concept –comparable to evolution provides a framework for –interpreting many aspects of Earth on a global scale –relating many seemingly unrelated phenomena –interpreting Earth history

Plate Tectonics and Earth Systems plate tectonics is driven by convection in the mantle – and in turn drives mountain building – and associated igneous and metamorphic activity Solid Earth Atmosphere arrangement of continents affects: – solar heating and cooling, – and thus winds and weather systems rapid plate spreading and hot-spot activity may release volcanic carbon dioxide and affect global climate

Plate Tectonics and Earth Systems continental arrangement affects ocean currents rate of spreading affects volume of mid- oceanic ridges and hence sea level placement of continents contributes to the onset of ice ages Hydrosphere Biosphere movement of continents creates corridors or barriers to migration, the creation of ecological niches, and transport of habitats into more or less favorable climates

Theory of Organic Evolution provides a framework for understanding the history of life Darwin’s On the Origin of Species by Means of Natural Selection, published in 1859 revolutionized biology

Central Thesis of Evolution all present-day organisms –are related –descended from organisms that lived during the past Natural Selection is the mechanism that accounts for evolution –results in the survival to reproductive age of those organisms best adapted to their environment

History of Life Fossils are the remains or traces of once- living organisms –demonstrate that Earth has a history of life –most compelling evidence in favor of evolution

Geologic Time human perspective –seconds, hours, days, years ancient human history –hundreds or even thousands of years geologic history –millions, hundreds of millions, billions of years

Geologic Time Scale resulted from the work of many 19th century geologists who –pieced together information from numerous rock exposures –constructed a sequential chronology based on changes in Earth’s biota through time the time scale was subsequently dated in years –using radiometric dating techniques

Geologic Time Scale

Uniformitarianism Uniformitarianism is a cornerstone of geology –present-day processes have operated throughout time –physical and chemical laws of nature have remained the same through time to interpret geologic events –we must first understand present-day processes and their results

How Does the Study of Historical Geology Benefit Us? survival of the human species depends on understanding how Earth’s various subsystems work and interact –how we consume natural resources and interact with the environment determines our ability to pass on this standard of living to the next generation –our standard of living depends directly on our consumption of natural resources that formed millions and billions of years ago study what has happened in the past, on a global scale, to try and determine how our actions might affect the balance of subsystems in the future

Present Note: Best data set available.

Latest Precambrian / Early Paleozoic Supercontinent Rodinia, centered about the south pole, breaks apart. North America (Laurentia), Baltica, and Siberia moved North. Marine Invertebrates. North America: arc on the south. Baltica and Siberia moved in from the SE. Texas ( Ma): Flat plain; remnants of eroded collisional belt (Llano). Shallow marine seas across much of Texas. Sandy sediment onshore, limestone offshore. Trilobites, brachiopods.

Latest Precambrian / Early Paleozoic Supercontinent Rodinia continues to break apart. Pieces move north. -Fish. -Glaciation. North America: Numerous plates and continental blocks move in from the south and east. The Taconic arc collides, forming the Taconic orogeny. Texas Ma: Shallow marine seas across much of inland Texas. Warm-water limestone. Corals, brachiopods.

Middle / Late Paleozoic Remains of Rodinia (Gondwana) move northward to collide with Laurasia -- creating the super continent Pangaea and the Tethys Ocean. First land-plants. Baltica collides with North America in the Caledonian-Acadian orogeny. Texas Ma: Shallow marine seas across much of west Texas - limestone. Corals, brachiopods.

Middle / Late Paleozoic Most drifting Rodinia blocks assembled into the super continent of Laurussia. Amphibians. Fish really get going. Ferns. Glaciation. North America: Caledonian-Acadian orogeny marks assemblage of Laurussia. Gondwana closed in from the south. An arc formed along western North America. Texas Ma: shallow marine sandstones and limestones in west Texas.

Middle / Late Paleozoic Gondwana, with a large, developing glacier, nears southern Laurussia. Fern-forests. North America: The Antler arc collides with western North America creating the Antler orogeny. Texas Ma: shallow marine seas inland. Shales and limestones.

Middle / Late Paleozoic Rodinia blocks of Laurussia and Siberia collide to form Laurasia. Reptiles. North America: Gondwana collides from the south. The resulting Appalachian, Ouachita, Marathon, Ural, Variscan, and Hercynian orogenies formed some of the largest mountains of all time. The Ancestral Rockies form. Texas Ma: Ouachita Mountains. Collision formed inland basins filled by seas. Limestone, sandstone, shale.

Latest Paleozoic / Early Mesozoic The supercontinent Pangaea dominates the Permian Earth, lying across the equator. Extinctions! Trilobites go away. North America: A new arc approaches western North America. A new spreading center forms as Cimmeria rifts from Gondwana and opens the Tethyian Ocean. The western fringe of Pangaea lay along the eastern margin of the Pacific "ring of fire” subduction zone. Texas Ma: Shallow marine inland of mountains. Reefs. Evaporites. Red shales.

Latest Paleozoic / Early Mesozoic Mammals. North America: Arc collision along western edge forms the Sonoman orogeny. As the Tethys Ocean expands, Cimmeria (Turkey, Iran, and Afghanistan) move northward towards Laurasia. Texas Ma: shales and sandstones in NW. Start opening the GOM - red sandstone, shale, evaporites.

Middle Mesozoic Pangaea rotates; different components at different rates / in different directions -- rifts form. Birds. North America: Southern North Atlantic Ocean opens, continuing west into the Gulf of Mexico. The Cordilleran arc develops along Pacific margin. Arc forms on western side. Nevadan orogeny begins. Cimmeria begins collision with Laurasia - Cimmerian orogeny. Texas Ma: Change in sediment direction. Shallow water deposition / evaporites in GOM.

Middle Mesozoic The Atlantic continues to expand as Pangaea breaks up. The Cimmerian orogeny continues. North America: Arcs and micro continents slam into western region. Laramide orogeny in Rockies. Texas Ma: Influx of sediment from Rockies. Shallow Cretaceous sea way across Texas. Shallow limestones, shales.

Late Cretaceous / Present Rifts separate Africa and South America and then India, Australia, Antarctica. North America rifts from Europe. Old Gondwana lands (Africa, India, Australia) move north toward Eurasia, closing the Tethys Ocean and forming the Alpine-Himalayan mountains. The Atlantic lengthens / widens, the Sevier orogeny continues, and the Caribbean arc forms. Texas Ma: continuing shallow limestone and shale deposition to the southeast (from Rockies).

Paleocene / Eocene Himalayan Orogeny. Alps and Pyrenees form. The modern patterns of Planet Earth appear. Atlantic continues to open. Rocky Mountains grow. Texas Ma: shale and sandstone in southeast region prograde shoreline (from the Rockies). Volcanic activity in Panhandle.

Oligocene and Miocene Orogeny continues in the Mediterranean region and India nears its junction with southern Asia. Antarctica isolated. Southwestern North America intercepts the East Pacific Rise and a great extensional event, the Basin and Range orogeny begins. Texas 35-5 Ma: continued sandstone/shale deposition and progradation of shoreline (erosion of Rockies)

Present Note: Best data set available.