© 2014 Pearson Education, Inc. Chapter 2 Lecture McKnight's Physical Geography 11e Lectures Chapter 13 An Introduction to Landform Study © 2014 Pearson Education, Inc. Andrew Mercer Mississippi State University

© 2014 Pearson Education, Inc. Learning Goals of This Chapter Describe the internal structure of Earth. Describe Earth's magnetic field. Define mineral, and explain why they are important. Describe the seven mineral families, and identify at least one mineral from each family. Describe quartz, and explain its importance. Differentiate between rock, bedrock, outcrop, and regolith. Identify the three rock classes or families, and explain how they form. Explain the classification of igneous rocks.

© 2014 Pearson Education, Inc. Learning Goals of This Chapter Describe igneous rock textures, and explain their relationships to magma and lava and the terms intrusive and extrusive. Identify and describe four intrusive igneous rocks and six extrusive igneous rocks. Explain the classification of sedimentary rocks. Explain the structure of sedimentary deposits. Identify and describe four detrital (clastic) sedimentary rocks and four chemical and organic sedimentary rocks. Explain the classification of metamorphic rocks. Explain the three types of metamorphism.

© 2014 Pearson Education, Inc. Learning Goals of This Chapter Explain "fracking." Identify and describe four foliated metamorphic rocks and four non-foliated metamorphic rocks. Explain the rock cycle and its significance. Differentiate between the continental and oceanic rocks. Explain isostasy and its significance. Define topography, landform, and geomorphology. Explain how structure, process, slope, and drainage act together to shape the landscape. Differentiate between internal and external geomorphic processes.

© 2014 Pearson Education, Inc. Learning Goals of This Chapter Differentiate between uniformitarianism and catastrophism. Explain with examples how "the present is the key to the past." Define geologic time, and explain the geologic time scale including the age of Earth. Using the concepts of uniformitarianism and geologic time explain the ways that internal and external processes are shaping Earth's surface. Explain the importance of scale and process in the study of geomorphology.

© 2014 Pearson Education, Inc. Introduction to Landform Study The Structure of Earth The Composition of Earth The Study of Landforms Some Critical Concepts Scale and Pattern

© 2014 Pearson Education, Inc. The Structure of Earth Understanding of Earth's structure based on minute fraction of total depth (less than 8 miles) Good deal of understanding inferred by geophysical means Four regions of Earth's interior

© 2014 Pearson Education, Inc. The Structure of Earth Crust –Depth of 5 km below ocean to near 20 km below land –Less than 1% of Earth's volume, 0.4% of Earth's mass –Moho discontinuity Mantle –Extends to depth of 2900 km (1800 miles) –Largest of four shells –Makes up 84% of total volume, 67% of total mass –Three sublayers Lithosphere Asthenosphere Rigid rocks – lower mantle

© 2014 Pearson Education, Inc. The Structure of Earth Outer core –Molten, extends to depth of 5000 km Inner core –Dense mass with radius of about 1450 km –Primarily made of iron/nickel or iron/silicate –Two zones combined make up 15% of Earth's volume and 32% of Earth's mass –Magnetic field of Earth controlled by outer core –Magnetic poles not the same as the axial poles Plate tectonics and the structure of Earth “Continental drift” Plate tectonics – continental-sized plates slide along the asthenosphere

© 2014 Pearson Education, Inc. The Composition of Earth Minerals – naturally formed compounds and elements of Earth Mineral characteristics –Solid –Found in nature –Inorganic –Specific chemical composition –Contains atoms that arrange in patterns to form crystals

© 2014 Pearson Education, Inc. The Composition of Earth Important crustal minerals –Silicates – combine oxygen and silicon, the most common elements in the lithosphere –Oxides – elements that are combined with oxygen –Sulfides – combination of sulfur and another element (i.e. pyrite – see figure)

© 2014 Pearson Education, Inc. The Composition of Earth Important crustal minerals (cont.) –Sulfates – contain sulfur and oxygen –Carbonates – light-colored minerals that are composed of a combination of carbon, oxygen and an element (e.g., limestone) –Halides – derived from word “salt,” salty minerals –Native elements – gold and silver

© 2014 Pearson Education, Inc. The Composition of Earth Common minerals on Earth

© 2014 Pearson Education, Inc. The Composition of Earth Rocks – composed of many minerals –Fewer than 20 minerals make up 95% of the composition of crustal rocks –Outcrops –Bedrock –Regolith –Petrology – characteristics of different rocks

© 2014 Pearson Education, Inc. The Composition of Earth The three classes of rocks

© 2014 Pearson Education, Inc. The Composition of Earth Igneous rocks –Igneous – “fiery inception” –Magma – molten rock beneath Earth's surface –Lava – molten rock when it flows onto Earth's surface –Pyroclastics –Classification of igneous rocks is based on mineral composition and texture –Texture based on how rocks cool

© 2014 Pearson Education, Inc. The Composition of Earth Two types of igneous rocks –Plutonic (intrusive) Rocks cool beneath Earth's surface Surrounding rocks insulate the magma intrusion, slowing cooling Individual minerals in a plutonic rock can grow to large size Granite

© 2014 Pearson Education, Inc. The Composition of Earth Two types of igneous rocks (cont.) –Volcanic (extrusive) Form on Earth's surface Cool rapidly Generally do not show individual mineral crystals, but can if the crystals are formed from shattered rock that was explosively ejected Basalt

© 2014 Pearson Education, Inc. The Composition of Earth Common igneous rocks

© 2014 Pearson Education, Inc. The Composition of Earth Sedimentary Rocks –External processes cause rock disintegration –Material transported by water as sediment –Over long periods, large amounts of sediment build to large thicknesses –Exert enormous pressure that causes particles in sediment to interlock –Chemical cementation takes place –Forms sedimentary rock –Strata – horizontal layers of sedimentary rock; sometimes tilted into vertical by Earth processes

© 2014 Pearson Education, Inc. The Composition of Earth An example of sedimentary rock

© 2014 Pearson Education, Inc. The Composition of Earth Two primary types of sedimentary rocks –Clastic Composed of fragments of preexisting rocks Also known as detrital rocks Shale is an example Conglomerate; composed of pebble-sized fragments –Chemical and organic sedimentary rocks Formed by precipitation of soluble materials or complicated chemical reactions Limestone and coal are examples Organic sedimentary rocks such as coal form from remains of dead plants and animals

© 2014 Pearson Education, Inc. The Composition of Earth The two primary types of sedimentary rocks; white rock is limestone, dark rock is shale

© 2014 Pearson Education, Inc. The Composition of Earth Metamorphic Rocks –Rocks that were originally igneous or sedimentary and have been changed by heat and pressure –Causes a “cooking” of rocks –Rearranges the crystal structure of the original rock –Contact metamorphism – rock contacts magma and is rearranged –Regional metamorphism – large volumes of rock are subjected to heat and pressure over long time scales –Limestone becomes marble, sandstone becomes quartzite, shale becomes slate

© 2014 Pearson Education, Inc. The Composition of Earth Schist – metamorphic rocks with narrow foliations Gneiss – broad, banded foliations

© 2014 Pearson Education, Inc. The Composition of Earth The rock cycle – processes where rocks can transition between the three rock types

© 2014 Pearson Education, Inc. The Composition of Earth Continental and ocean floor rocks –Sedimentary rocks make up 75% of the continents –Sedimentary cover is not thick –Continental crust – sial (silicon and aluminum) –Ocean floor crust – sima (silicon and magnesium) –Ocean lithosphere is more dense than continental lithosphere –Ocean crust can be subducted into the athenosphere –Isostasy – recognition of differences between oceanic crust, continental crust, and mantle

© 2014 Pearson Education, Inc. The Composition of Earth Isostasy – recognition of differences between oceanic crust, continental crust, and mantle

© 2014 Pearson Education, Inc. Some Critical Concepts Internal and External Geomorphic Processes –Internal – originate from within Earth, increase relief of land surface –External – originate from sources above the lithosphere, such as the atmosphere or oceans; decrease relief of land surface

© 2014 Pearson Education, Inc. Some Critical Concepts Uniformitarianism –“The present is the key to the past” –Past thinking believed catastrophism, catastrophes shaped the land surface –Processes that shaped the landscape of the past are the same that will shape the future Geologic time –Vast periods of time over which geologic processes operate

© 2014 Pearson Education, Inc. Some Critical Concepts An example of scale – five perspectives of Horseshoe Park

© 2014 Pearson Education, Inc. Some Critical Concepts The Pursuit of Pattern – major landform assemblages of the world

© 2014 Pearson Education, Inc. Summary Earth's structure is presumed based on geophysical research. Earth's interior consists of four regions. Earth's composition consists of elements or compounds of elements called minerals. Seven primary types of minerals exist. Rocks are composed of minerals. Igneous rocks are those formed by cooling and solidification of molten rock. Plutonic rocks are those that form within Earth.

© 2014 Pearson Education, Inc. Summary Volcanic rocks form on Earth's surface. Sedimentary rocks form as a result of transport of mineral material by water. Two primary types of sedimentary rocks, clastic and chemical/organic sedimentary rocks. Metamorphic rocks are igneous or sedimentary rocks that have been drastically changed by heat and/or pressure. Two primary types, schist and gneiss. The rock cycle is the transition cycle through the different rock types.

© 2014 Pearson Education, Inc. Summary Continental and ocean floor rocks possess different characteristics that are important in geophysical processes. Isostasy is the recognition of the differences between continental crust, oceanic crust, and mantle. Landforms are characterized by structure, process, slope, and drainage. Internal and external geomorphic processes are responsible for the relief of Earth. Uniformitarianism allows us to use geologic time to infer what happened in the past based on the present.