What is a pillow like structure?
A structure, observed in certain extrusive igneous rocks, that is characterized by discontinuous pillow-shaped masses ranging in size from a few centimeters to a meter or more in greatest dimension (commonly between 30 cm and 60 cm).
What is ball and pillow structure in geology?
“Ball & pillow” is a type of soft sediment deformation, when fresh sand is deposited atop soft, squishy mud. The density inversion triggers a load/sag phenomenon, and the sand pooches downward while the mud squooches up alongside, folding the sand into a shape much like an up-side-down mushroom cap.
What is a flame structure in geology?
A flame structure is a type of soft-sediment deformation that forms in unconsolidated sediments. The weight of an overlying bed forces an underlying bed to push up through the overlying bed, generally when both strata are saturated with water. The resulting pattern (in cross section) may resemble flames.
What is convolute bedding?
Convolute bedding forms when complex folding and crumpling of beds or laminations occur. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer. Convolute laminations are found in flood plain, delta, point-bar, and intertidal-flat deposits.
How are pillow structures formed?
Pillow lavas form when eruptions occur underwater, particularly when there is a relatively low eruption rate. Water rapidly quenches the outer surface, but the pillow continues to inflate as lava continues to be emitted so that it forms a pillow-like structure.
What is called a pillow?
A pillow is a soft cushion that a person puts under their head when they are sleeping in a bed. Standard pillows for use on beds Not a pillow as the word is used in English. Instead, this might be called a bolster.
What is pillow structure in petrology?
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one meter in diameter.
What causes ball and pillow structure?
Ball-and-pillow deformations are a result of a physical shock that has been applied to unconsolidated sediment. This shock causes rupturing to occur in the sedimentary rock layer, which induces instability. Individual lobes caused by this unstable state break off and move downward, settling into the underlying layers.
What is the pillow structure of igneous rocks?
Pillow structures
These are aggregates of ovoid masses, resembling pillows or grain-filled sacks in size and shape, that occur in many basic volcanic rocks. The masses are separated or interconnected, and each has a thick vesicular crust or a thinner and more dense glassy rind.
Where do flame structures form?
Flame structures; they are mainly formed in sands, muds, and marls. The structures range from 5 to 30 cm in size (Figure 2) and are developed by mudstones which are injected into overlying sandstones. This injection is the result of large differences in dynamic viscosity between sediment layers.
What is cross bedding in geology?
In geology, cross-bedding, also known as cross-stratification, is layering within a stratum and at an angle to the main bedding plane. The sedimentary structures which result are roughly horizontal units composed of inclined layers.
Where are flame structures found?
Flame structures found in sedimentary rocks may have formed from liquefaction and gravitational instability when the sediments were still unconsolidated and were subject to shaking caused by earthquakes.
What is the ball and pillow sedimentary structure?
ball and pillow structure A sedimentary structure occurring on the base of some sandstones which are interbedded with mudstones, and characterized by globular protrusions and isolated pillows of sandstone found in the underlying mudstone.
What are bedding structures?
Bedding Plane Structures are commonly used as paleocurrent indicators. They are formed when sediment has been deposited and then reworked and reshaped. They include: Sole markings form when an object gouges the surface of a sedimentary layer; this groove is later preserved as a cast when filled in by the layer above.
What is a slump structure?
A sedimentary structure consisting of overturned folds, formed by the mass sliding of the semi-consolidated sediment downslope under the influence of gravity.
Why is it called pillow?
The word pillow comes from Middle English pilwe, from Old English pyle (akin to Old High German pfuliwi) and from Latin pulvinus. The first known use of the word pillow was before the 12th century.
How are pillow shaped rocks formed?
Pillow basalt is a volcanic igneous rock that forms when lava of basaltic compositionis erupted underwater. The rapid cooling of the lava by cold water on all sides forms the pillow-shaped bodies, which can then break open and extrude more of the hot lava from inside.
How are pillow structures in volcanic rocks produced?
Pillow lavas typically form along submarine volcanic vents, where fresh basaltic lava tumbles over the seafloor. When molten lava oozes slowly into water, the outer–most layer quenches instantly, forming a rind of hot glass over a bulb of molten rock.
Who invented pillow?
Answer and Explanation: Pillows were invented by the Mesopotamians in 7000 BC. Unlike the modern ones, pillows of the ancient world were made of stone. They were a bit elevated so that the head could be kept some distance away from the ground.
Why is it called a husband pillow?
The term “husband pillow” refers to the cushion's wrap-around design, which reminds many users of a body hug from a significant other. Husband pillows allow users to assume a more natural upright position on a bed, floor, or couch for activities other than sleeping.
Is pillow a type of cushion?
Cushions are more geometrically cube-like in shape, with 6 sides and distinct edges. Pillows are two sided, softer in form, and are filled with loose fiber instead of structured foam inserts.
What is the pillow structure of lava?
Pillow lavas are bulbous, spherical, or tubular lobes of lava. They form during eruptions with relatively low effusion rates. Slow extrusion gives enough time for a thick crust to form on all sides of a pillow lobe, and prevents individual pillows from coalescing into a sheet.
Why do pillow basalts form?
Basalt "pillows" form when lava cools quickly under water. The lack of bubbles in the lava suggests that the rock crystallized on the ocean floor under the pressure of deep water (preventing bubbles from forming in the lava).
What is the mineralogy of pillow basalt?
The pillow basalts consist of aphyric (<1% phenocrysts) to moderately phyric (2%-10% phenocrysts) plagioclase ± olivine ± pyroxene or olivine ± plagioclase basalts and show a low degree of vesicularity (<2%), with vesicles having diameters generally <1 mm.
What are the deformation structures?
Deformation structures include faults and folds. The folds are commonly on a centimeter scale, and fold axial planes are commonly subhorizontal and parallel to bedding. In interval 210-1276A-14R-2, 8-32 cm, a well-developed chevron fold is observed (Fig.
What are the soft sediment structures?
Many soft-sediment deformation structures are related to the presence of a gravitationally unstable profile of bulk density within a sedimentation unit or sequence of units—for example, convolute lamination, load casts, pseudo-nodules, ball-and-pillow, heavy mineral sags and drops, and dish structures.
Why do pillow lavas have their characteristic pillow shape?
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava under water, or subaqueous extrusion.
Are pillow basalts fine-grained?
The glassy crust has broken off the rounded surface of this pillow, exposing the dark, fine-grained basalt beneath. The radial pattern of fractures on the side is typical of pillows that cool quickly from their outer surface ot their center, quenched by cold seawater.
Is pillow basalt intrusive or extrusive?
Basalt (UK: /ˈbæsɔːlt, -əlt/; US: /bəˈsɔːlt, ˈbeɪsɔːlt/) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon.
What is the texture of a pillow basalt?
This "pillow" texture is very common in underwater basaltic flows and is diagnostic of an underwater eruption environment when found in ancient rocks. Pillows typically consist of a fine-grained core with a glassy crust and have radial jointing. The size of individual pillows varies from 10 cm up to several meters.
How do flame structures form?
Flame structures are formed when a denser sediment, (typically sand) is deposited on top of a less dense sediment (typically mud). The difference in density forces the mud to flow upward in what are known as diapirs, producing a distinctive flame-like structure in which the "flames" are always at the top.
How are load casts formed?
Load casts develop by the differential sinking of the sediment, while still soft, into less dense sediment below. Load 'casts' are not strictly casts, as they do not infill an existing depression as in the case of flute casts (see flute mark).
How do gutter casts form?
The gutter casts form by eroding currents. Several models have been proposed (Myrow 1992), but the most appropriate appears to be helical flow vortices. Gutter casts characterise sedimentation in the bypass zone, and develop during storms when strong currents transport sediment to the outer shelf (Perez-Lopez 2001).
What is bedding rocks?
Bedding is the arrangement of sedimentary rocks in beds or layers of varying thickness and character.
What creates cross-bedding?
Cross beds form from running water. As the water flows, it creates bedforms, such as ripples or dunes, on the floor of the channel. Sediment deposited on the downcurrent side of these bedforms is deposited at an angle--not horizontally.
What is bedding and foliation?
“Bedding” is a term used for sedimentary rocks that are deposited in layers, and this layering is often seen as parallel layers of grains. Bedding. Foliation is the result of moderately high grade metamorphism which causes the long axes of crystals to re-align themselves perpendicular to the stress field.: → ||| ←
What is convoluted bedding?
Convolute bedding forms when complex folding and crumpling of beds or laminations occur. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer. Convolute laminations are found in flood plain, delta, point-bar, and intertidal-flat deposits.
How does trough cross bedding form?
Trough cross-beds form where higher flow intensities are present (Rubin, 1987) which cause erosional scours at the base of the slip slope of transverse bedforms (Pettijohn et al., 1987).
How are graded beds formed?
Graded beds form when a steep pile of sediment on the sea floor (or lake floor) suddenly slumps into a canyon or off a steep edge. As the sediment falls, water mixes in with it, creating a slurry of sediment and water that flows quickly down a sloping bottom. When the bottom levels out, the flow begins to slow.
What is a pillow structure in geology?
volcanoes have steep sides of pillow lavas—sacklike structures that form when flows of basaltic lava are extruded into the ocean, a deep lake, or a water-filled cavern within ice. These pillow structures are capped by several tens of metres of broken lava fragments from explosive shallow-water eruptions.
Is bedding a sedimentary structure?
Bedding (also called stratification) is one of the most prominent features of sedimentary rocks, which are usually made up of 'piles' of layers (called 'strata') of sediments deposited one on top of another.
What is sedimentary bedding?
Any layer of rock in a sedimentary sequence that can be distinguished from the layers above and below is a bedding plane. Bedding planes, also called beds or strata (singular: stratum) are the simplest sedimentary structures and the smaller lithostratigraphic unit used by geologists to describe sedimentary formations.
What are the 4 types of sedimentary structures?
Raindrop impressions tend to be found in fine-grained rocks like siltstones and shale but not in coarser-grained sandstones. The impressions likely represent the end of a rainstorm as rain is letting up because any previously formed impressions would be destroyed by subsequent rainfall.
Where are raindrop impressions found?
A sedimentary structure characterized by a concave-upwards erosion surface cut into the underlying bed by a high-velocity flow of water, and filled by a sediment, which is usually coarse, during the waning stage of the flow that cut the scour.
What is a scour and fill structure?
Three types of Slump can be observed - Shear Slump, Collapse Slump, and True Slump. True Slump refers to a general drop of the concrete mass evenly all around without disintegration.
What are the 4 types of slump?
Concrete slump plays a crucial role in the construction industry, as it determines the consistency and workability of concrete. Whether you're constructing a high-rise building or a bridge, understanding the meaning of concrete slump is essential for your project.
What is the purpose of a slump?
a bag or case made of cloth that is filled with feathers, down, or other soft material, and is used to cushion the head during sleep or rest. anything used to cushion the head; headrest: a pillow of moss.
What is called pillow?
It seems as though in North America, the word “pillow” is used more often than the word cushion. Most of us use the word pillow interchangeably, no matter if we are talking about a pillow for your bed or a pillow that is on your couch as a form of home décor.
What do Americans call pillows?
A sedimentary structure occurring on the base of some sandstones which are interbedded with mudstones, and characterized by globular protrusions and isolated pillows of sandstone found in the underlying mudstone.
What is the ball and pillow sedimentary structure?
Examples include glaciovolcanic pillow mounds in British Columbia, which are formed solely of pillow lava extruded under ice sheets that may have been >2 km thick, and pillow-lava centers draped unconformably by agglutinate at Seal Nunataks, Antarctica, which formed within an ice sheet >600 m thick.
What is an example of pillow lava?
Pillow lavas form when eruptions occur underwater, particularly when there is a relatively low eruption rate. Water rapidly quenches the outer surface, but the pillow continues to inflate as lava continues to be emitted so that it forms a pillow-like structure.
What is a pillow volcano?
What do pillow structures indicate about the environment of volcanism? As the lava erupts into water, it cools rapidly forming a distinctive feature known as pillow structure. Basaltic rocks generally occur as pillow-shaped, rounded masses closely fitted together. Pillow structures indicate underwater volcanism.
What do pillow structures indicate about the environment of volcanism?
a cloth cover for a pillow that can easily be removed and washed.
What's a pillow case?
Pillows in ancient times were a lot of things, but soft wasn't one of them. They were often made of stone or wood, carved into a cradle shape to hold the neck in place off of the ground. The oldest known pillow dates back to Mesopotamia over 9,000 years ago.
Did ancient humans have pillows?
The Boyfriend Body Pillow is akin to a virtual hug pillow; a thick, ultra-soft fluffy friend culled from pure cotton that even comes complete with an extended arm and is a virtual real man. Lose yourself in a warm, wonderful embrace of a pillow; one never too weary to cuddle and comfort you!
What is boyfriend pillow?
Pillow talk is the relaxed, intimate conversation that can occur between sexual partners after sexual activity, usually accompanied by cuddling, caresses, kissing, and other physical intimacy.
What is a pillow romance?
The versatile standard pillow has a traditional rectangular shape. It is the most common option, and it is readily available with different sizes, lofts, fill materials, and firmness levels. A standard pillow accommodates any sleep position.
What is the normal pillow shape?
A standard pillow measures 20 by 26 inches (51 x 66 cm). Like the name suggests, this pillow size is universal and can fit on any sized bed, from twin to California King. One standard pillow fits comfortably on a twin or twin XL bed, and two standard pillows will sit nicely side by side on a full or queen size bed.
What is a pillow dimension?
a cloth cover for a pillow that can easily be removed and washed.
What's a pillow case?
A firm pillow is, as the name suggests, quite hard. It doesn't give much when you press it down with your hand. This might sound uncomfortable, but a firm pillow can be quite comfortable for people. The hard surface provides a stable base for your head and prevents your neck from moving around too much as you sleep.