Tertiary period (tûr`shēĕr'ē), name for the major portion of the Cenozoic era Cenozoic era (sēnəzō`ĭk, sĕn–)
..... Click the link for more information. , the most recent of the geologic eras (see Geologic Timescale Geologic Timescale
Era Period Epoch Approximate duration

(millions of years)

Approximate number of years ago

(millions of years)

..... Click the link for more information. , table) from around 26 to 66 million years ago. The name Tertiary was first applied about the middle of the 18th cent. to a layer of deposits, largely unconsolidated sediments, geologically younger than, and overlying, certain other deposits then known as Primary and Secondary. Later (c.1830) a fourth division, the Quaternary, was added. Although these divisions of the earth's crust seemed adequate for the region to which the designations were originally applied (parts of the Alps and plains of Italy), when the same system was later extended to other parts of Europe and to America it proved to be inapplicable. It was realized that one scheme of classification could not be applied universally: The names Primary and Secondary were generally abandoned; Tertiary and Quaternary were, and still are, used, but other geologic literature substitutes other names, including the Palaeogene and Neogene. The main divisions of the Tertiary are the Paleocene Paleocene epoch (pā`lēəsēn')
..... Click the link for more information. , Eocene Eocene epoch (ē`əsēn'), second epoch of the Tertiary period in the Cenozoic era of geologic time, from approximately 54.
..... Click the link for more information. , Oligocene Oligocene epoch (ŏl`əgōsēn')
..... Click the link for more information. , Miocene Miocene epoch (mī`əsēn)
..... Click the link for more information. , and Pliocene epochs Pliocene epoch (plī`əsēn), fifth epoch of the Cenozoic era of geologic time (see Geologic Timescale , table), from 5.
..... Click the link for more information. . Sometimes the Paleocene is included in the Eocene. At the beginning of the Tertiary, the outlines of the North American continent were very similar to those of today; by the close of the period, Europe also had emerged substantially in its present form. Marine submergences in Europe were moderately extensive, but in North America they never went beyond the Atlantic, Gulf, and Pacific coasts and the lower Mississippi valley. These inundations took place chiefly in the Eocene, Oligocene, and Miocene epochs, the continents being generally emergent in the Pliocene epoch. The Tertiary formations of either unconsolidated sediments or quite soft rocks are widespread. In the Tertiary, Gondwanaland finally split completely apart, and India collided with the Eurasian plate (see plate tectonics plate tectonics, theory that unifies many of the features and characteristics of continental drift and seafloor spreading into a coherent model and has revolutionized geologists' understanding of continents, ocean basins, mountains, and earth history.
..... Click the link for more information. ). The previously existing mountain ranges of North America were again elevated, the Alps, Pyrenees, Carpathians, and other ranges were formed in Europe, and in Asia the Himalayas arose. Widespread volcanic activity was prevalent. At the beginning of the period the mammals replaced the reptiles as the dominant animals; each epoch was marked by striking developments in mammalian life. Modern types of birds, reptiles, amphibians, fishes, and invertebrates either were already numerous at the beginning of the period or appeared early in its history.

Tertiary Period

Interval of geologic time, 65–1.8 million years ago. It constitutes the first of the two periods of the Cenozoic Era, the second being the Quaternary. The Tertiary has five subdivisions: (from oldest to youngest) the Paleocene, Eocene, Oligocene, Miocene, and Pliocene epochs. During most of the Tertiary, the spatial distribution of the major continents was largely similar to that of today. Emergence and submergence of land bridges between continents critically affected the distribution of both terrestrial and marine animals and plants. Virtually all the existing major mountain ranges were formed either partly or wholly during the Tertiary.