The world, Miocene, 20 Ma, Global Paleogeographic Views of Earth History, NAU
The world, Miocene, 20 Ma, Paleogeography Through Geologic Time, NAU
The World, Miocene, 14 Ma, PALEOMAP Project
North America, Miocene, Langhian Stage, 15 Ma, Paleogeography and Geologic Evolution of North America, NAU
North America, Miocene, Tortonian Stage, 8 Ma, Paleogeography and Geologic Evolution of North America, NAU
North America, Miocene, 15 Ma, Regional Paleogeographic Views of Earth History, NAU
Southwestern U.S., Miocene, 20-15 Ma, Geologic History of Western US, NAU (third map)
Miocene, Palæos
Miocene, Wikipedia
The Miocene Epoch, University of California Museum of Paleontology
Geologic Time Table, Seafriends
See general sources above.
Miocene, ~ 15 Ma, PALEOMAP project
Miocene Epoch: Life, University of California Museum of Paleontology
Miocene Mammal Mapping Project (MIOMAP), University of California Museum of Paleontology
Miocene Life category, Wikipedia
Terrestrial Life during the Miocene, and Marine Life in the Miocene, Smithsonsian National Museum of Natural History
Miocene Epoch, Deep Time, Evolution, PBS
Rusinga Island fossil site, Lake Victoria, Africa, Wikipedia
Agate Fossil Beds National Monument, Nebraska, Wikipedia
Middle Miocene Calvert Formation, Calvert Cliffs State Park, Maryland, Wikipedia
Gray Fossil Site, Tennessee, Wikipedia
John Day Fossil Beds National Monument, Oregon, Wikipedia
Alcoota Fossil Beds, Australia, Wikipedia
Bullock Creek Fossil Site, Australia, Wikipedia
Riversleigh Fossil Site, Australia, Wikipedia
The Miocene marks the beginning of the Neogene Period.
The cooling period that lasted for most of the Oligocene Epoch reverses near its end. The first half of the Miocene is relatively warm. Half way into the Miocene a sharp decrease in global temperature occurs, and the cooling trend that began in the Eocene continues. The current Antarctic ice sheet formed at this time.
South America continues to move north towards North America, but the Isthmus of Panama still does not exist. Ocean waters still circulate between the Atlantic and the Pacific, but the gap becomes smaller.
India and Africa continue to move north into Eurasia, and the mountain building (Alpine orogeny) that began in the Eocene continues. Africa and the Arabian plate become joined to Asia.
The Yellowstone hotspot formed about 17 Ma near the eastern Oregon-Nevada border. As the North American Plate moved west over it during the Miocene, calderas formed across Idaho. The calderas and volcanic fields formed by the Yellowstone Hotspot include: the McDermitt volcanic field (Miocene), Owyhee-Humboldt volcanic field (Miocene), the Bruneau-Jarbidge caldera (Miocene), Twin Falls volcanic field (Miocene), Picabo caldera and Craters of the Moon (Miocene-Holocene), Heise volcanic field (Miocene-Pliocene), Island Park Caldera (Pliocene-Pleistocene), Henry's Fork Caldera (Pleistocene), and today's Yellowstone Caldera in Yellowstone National Park.
Volcanism occurs along the Sierra Nevada range in California after 20 Ma. Later, about 10 Ma, uplift occurs along the Sierra fault, and the mountains begin to rise higher. Streams and rivers begin to cut down into the Sierra Nevada Batholith formed during the Jurassic Period as part of the Nevadan orogeny. The granite is exposed as the first large valleys are carved out. The mountains and valleys of the Basin and Range Province form.
Volcanism that started in the Oligocene Epoch continues in San Diego County in the Jacumba Volcanics area.
The San Andreas Fault forms, and the Farallon Plate starts to divide into the Cocos Plate and the Juan de Fuca Plate.
Apes first appear late in the Oligocene or in the Miocene. Genetic evidence indicates that the ancestor of hominids (great apes and all human species) lived in the middle Miocene. Two African species from the late Miocene, Sahelanthropus tchadensis and Orrorin tugenensis, may be early ancestors of humans.
As the earth continued cooling, more deserts and arid areas formed. This is because cool air holds less water than warm air. Australia moved north, and this also encourged formation of its deserts.
Grasslands first form on land and kelp forests form in the oceans.
The Bering Sea disappears and a Bering land bridge forms between Asia and Alaska.
Near the end of the Miocene (after 6 Ma), the western end of the Mediterranean was closed off from the Atlantic Ocean. This was probably due to the uplift of Europe and North Africa, and changes in climate. The Mediterranean may have completely evaporated. This is called the Messinian salinity crisis. Large amounts of salt, gypsum, and other evaporated minerals were deposited. When the ocean water began to flood in again, a huge waterfall formed, larger and more powerful than any today.
© 2009, Mr. Varner.
