seafloor spreading
21Atlantic Ocean — an ocean bounded by North America and South America in the Western Hemisphere and by Europe and Africa in the Eastern Hemisphere. ab. 31,530,000 sq. mi. (81,663,000 sq. km); with connecting seas ab. 41,000,000 sq. mi. (106,100,000 sq. km);… …
22Mid-ocean ridge — Oceanic ridge, including a black smoker A mid ocean ridge is a general term for an underwater mountain system that consists of various mountain ranges (chains), typically having a valley known as a rift running along its spine, formed by plate… …
23Ordovician Period — Interval of geologic time, 490–443 million years ago, the second oldest period of the Paleozoic Era. It follows the Cambrian and precedes the Silurian. During the Ordovician, many of the landmasses were aligned in the tropics. Life was dominated… …
24Earth and Space Sciences — ▪ 1996 Introduction GEOLOGY AND GEOCHEMISTRY In 1995 significant developments took place in the realm of geologic mapping, which provides the foundation for the presentation and comparison of data in the Earth sciences. The most important… …
25undersea exploration — Introduction the investigation and description of the ocean waters and the seafloor and of the Earth beneath. Primary objectives and accomplishments Included in the scope of undersea exploration are the physical and chemical… …
26Ophiolite — Ordovician ophiolite in Gros Morne National Park, Newfoundland. An ophiolite (  / …
27marine geology — marine geologist. the branch of geology dealing with the rocks, sediments, and processes of the floors and margins of the oceans. * * * or geologic oceanography Scientific discipline concerned with all geologic aspects of the continental shelves… …
28Plattentektonik und Kontinentaldrift — Über zwei Jahre lang machte der Vulkan Soufrière, einer der sieben aktiven Vulkane auf der zu den Kleinen Antillen gehörenden Insel Montserrat den 12 000 Bewohnern dieser britischen Kronkolonie zunehmend klar, wer ihr eigentlicher Herr ist. Er… …
29Oceanic trench — Oceanic crust is formed at an oceanic ridge, while the lithosphere is subducted back into the asthenosphere at trenches. The oceanic trenches are hemispheric scale long but narrow topographic depressions of the sea floor. They are also the… …
30Precambrian time — Interval of geologic time from с 3. 8 billion years ago, the age of the oldest known rocks, to 544 million years ago, the beginning of the Cambrian Period. This interval represents more than 80% of the geologic record and thus provides important… …
