Presentation on theme: "Physical Geography: Landforms. Overview Geologic Time Movements of the Continents Earth Materials Tectonic Forces Weathering and Erosion Processes Erosional."— Presentation transcript:
Overview Geologic Time Movements of the Continents Earth Materials Tectonic Forces Weathering and Erosion Processes Erosional Agents and Deposition
Geologic Time Pretend the age of the earth (4.6+ billion years) is compressed into one calendar year. January 1 - Earth and planets formed Early March - liquid water stands in pools. Late March - earliest life July - oxygen is important part of atmosphere October 25 – multi-cellular organisms Late November - plants and animals abundant December 15 to 25 - dinosaurs arise and disappear 11:20 pm, December 31 - Humans appear One second before midnight - Automobile invented
What is ‘tectonics’? From Greek ‘tektonikus’ meaning building or construction Plate tectonics refers to the process of earth crust formation, movement, and destruction.
What is a ‘Plate?’ Lithospheric plate: crust + upper mantle Aesthenosphere: plastic mantle
History of Plate Tectonics ‘Fit’ of coastlines recognized early –Sir Francis Bacon (1600s) No mechanism for motion
1915 Alfred Wegener proposes theory of continental drift. Supercontinent Pangaea (‘all-earth’) [225mya]. Fragmentation and drift to current positions.
Plate Tectonics Theory Continental Drift + Sea Floor Spreading + new data Theory of Plate Tectonics
Plate Tectonics Theory Plate boundaries: main location for Earth’s volcanic and earthquake activity. This is main place where mountains are created. Type of plate boundary determines activity. 3 types –diverging (spreading) –converging (colliding) –transform (sliding past each other)
Earth Materials Formation of Earth Three major rock types –Igneous –Sedimentary –Metamorphic
Formation of the Earth’s Interior @5 bya, plantesimals (meterorites,icy comets) collide heat released (Kinetic energy to thermal energy) Entire planet melts (still cooling today) Gravity sorts materials by density –Fe in center –Si and O compounds towards surface
General trends: temperature, density Horizon composition, behavior The Earth’s Interior Distance: 6730 km (3963 miles)
Igneous Rocks Igneous (ignus = fire) Formed from the cooling of molten rock (magma/lava), a process called crystallization. –Slow cooling larger crystals > dense rock –Rapid cooling small crystals > lighter rock
Two classes of igneous rocks –intrusive: formed inside the Earth –extrusive: formed at Earth’s surface
Igneous Extrusive Landscapes Volcanic neck and dike: Shiprock, NM Volcanic cones, obsidian flow: Mono Craters, CA Volcanic Crater and Cinder Cone: Indonesia
Igneous Extrusive Rocks Cools rapidly - exposed to surface No visible crystals Examples - rhyolite - andesite -basalt
Some unique volcanic rock types Pumice (vesicular) - sometimes so light it floats! Obsidian –glassy, ‘curved’ fracturing –used for arrowheads by Native Americans
Your consent to our cookies if you continue to use this website.