1.2 The Rock Cycle Flashcards
What is meant by the term diagenesis?
Diagenesis includes all processes that occur in sediments at low temperatures and pressure at or near the Earth’s surface.
What is meant by the term metamorphism?
The changing of rocks in the Earth’s crust by heat and/or pressure and/or volatile content.
Metamorphism is isochemical (the chemical composition does not change) and occurs in the solid state.
What are igneous rocks?
rocks that have crystallised from magma
What is partial melting?
when only a portion of rock in the lower crust or upper mantle is melted
What is recrystallisation?
the solid state process that changes minerals into new crystalline metamorphic minerals
What is crystallisation?
Crystallisation occurs during the cooling of magma or lava so that solid mineral crystals form.
What is meant by burial as a process within the rock cycle?
the covering of sediment by younger layers of sediment
What is a sedimentary rock?
A rock composed of fragments that have been deposited, compacted and cemented.
What is a clast?
a fragment of broken rock produced by mechanical weathering and erosion
What is magma accumulation?
magma collecting within a magma chamber
What is an intrusion?
Igneous rock that has formed below the Earth’s surface, where magma is forced into pre-existing rocks.
What is extrusion?
The emission of magma onto the Earth’s surface where it forms a lava flow.
What is foliation?
Foliation is a texture in metamorphic rocks formed by the preferred alignment of flat/tabular minerals.
What is deposition?
the laying down of sediment that occurs when a transporting agent loses energy
What is weathering?
the breakdown of rocks in situ
What is erosion?
the removal of weathered material, usually by the physical action of transported fragments
What is transport?
the means by which weathered material is moved from one place to another by water, wind, ice or gravity
What is uplift?
the return of buried rocks to the Earth’s surface by tectonic forces
Describe the boundary between the diagenesis of sediments and metamorphism.
The boundary is gradational - a sedimentary shale grades into a metamorphic slate; the change is gradual and a rock can exist at stages along a spectrum from true shale to true slate.
What occurs at the boundary between igneous and metamorphic rocks?
partial melting
Which rocks form at low pressures and low temperatures?
sedimentary rocks
Which rocks form at high pressure?
metamorphic rocks
Which rocks form at very high temperatures or high temperature and greater than 200 MPa?
igneous rocks
What is the main observable difference between an igneous rock formed at greater depth and one formed close to or at the surface?
igneous rocks formed at greater depth have larger crystals
Which group of rocks will not contain calcite: igneous, metamorphic or sedimentary?
igneous
Which mineral is indicative of metamorphism: mica, augite or garnet?
garnet
Which common igneous mineral is not found in sedimentary or metamorphic rocks: K-feldspar, olivine or augite?
olivine
If a rock is observed to have beds (layers), is it igneous, sedimentary or metamorphic?
sedimentary
If a rock is observed to have foliation (alignment of minerals), is it likely to be igneous, sedimentary or metamorphic?
metamorphic
