Lesson 3 – Key Terms

Write the following Key Terms and their definitions in the Key Terms portion of your notebook. The definitions are found in the glossary of your textbook and/or the chapter. Once you have finished, take the Key Terms quiz.

• Alpha particles – A highly energetic radioactive decay product consisting of two protons and two neutrons (essentially a helium nucleus without electrons).
• Aphanitic – Refers to the fine crystal size (<1 mm) in igneous rocks.
• Aureole – A rind of un-melted, but altered baked material that surrounds a pluton.
• Bowen’s reaction series – A series of chemical reactions that happen within magmas leading to the crystallization of the magma. It is named in honor of N.L. Bowen.
• Compaction – When sediment is turned into sedimentary rock it must be squeezed (or compacted) to drive water out and reduce pore space.
• Convection – The transfer of heat through the motion of a fluid. This is driven by gravity and differences in density.
• Country rocks – The rocks that surround a cooling igneous pluton.
• Creation week rocks – Rocks that were either called into existence early in the Creation Week (Days 1-3) or formed by processes that were unique to the Creation Week.
• Dewatering – The removal of water from sedimentary rock as the result of compaction (squeezing).
• Extrusive igneous rock – Rock that forms as the result of volcanic activity. The rock is extruded from volcanoes.
• Igneous rock – Any rock that has crystallized from liquid or molten rock.
• Intrusive igneous rock – A rock that has formed from liquid rock “intruding” into pre-existing country rock.
• Lava – Liquid rock that is found above the surface of Earth.
• Lithification – The hardening process that turns sediment into sedimentary rock.
• Magma – Liquid or molten rock below the surface of Earth.
• Magmatic water – Water that is contained within hot liquid rock (magma).
• Meteoric water – Water derived from precipitation in the atmosphere. Much of this water can infiltrate into the ground and become groundwater.
• Pegmatitic – A crystalline igneous rock texture where the mineral grains are larger than 30 mm in diameter.
• Phaneritic – A crystalline igneous rock texture where the mineral grains are between 1–30 mm in diameter.
• Pluton – A large underground body of liquid magma that cools to form an igneous rock.
• Polonium – A radioactive element that is a decay product of uranium.
• Porphyritic – An igneous rock that has two distinct grain sizes (large and small).
• Pyroclastic – “Broken bits of fiery rock” sourced from volcanoes.
• Radiohalo – A circular (spherical) bulls-eye-like scar that is produced by numerous alpha particles emanating from a radioactive point source. Commonly they occur surrounding zircon grains in sheets of biotite in granite.
• Rock cycle – A hypothetical process that shows how igneous, metamorphic and sedimentary rocks are related to each other.
• Sediment – Loose particles that have been derived from the weathering of rock (mud, silt, sand, etc.)
• Vesicular – A texture of igneous rocks describing the large numbers of holes in the rock. The holes develop as the result of volcanic gases making frothy bubbles in lava as it was cooling.
• Volcanic igneous rock – Sometimes referred to as extrusive igneous rock because the rock was “extruded” out of a volcano.
• Weathering – A mechanical or chemical process that breaks a larger rock down into smaller pieces or its chemical constituents.