What Does Hummocky Cross Stratification Indicate?

Hummocky beds vary in thickness from a few centimetres to 5 or 6 m; bed sets may be tens of metres thick. Hummocky stratification apparently is formed most commonly by redeposition below normal fair-weather wave base of fine sand delivered offshore by flooding rivers and scour of the shoreface or shoals by large waves.

What causes hummocky?

An extremely irregular surface may be called hummocky. An ice hummock is a boss or rounded knoll of ice rising above the general level of an ice-field. Hummocky ice is caused by slow and unequal pressure in the main body of the packed ice, and by unequal structure and temperature at a later period.

What causes cross-bedding?

Cross-bedding is formed by the downstream migration of bedforms such as ripples or dunes in a flowing fluid. … Cross-bedding can form in any environment in which a fluid flows over a bed with mobile material. It is most common in stream deposits (consisting of sand and gravel), tidal areas, and in aeolian dunes.

How is cross stratification formed?

Cross stratification forms under laminar flow conditions, either in water (rivers, deltas, beaches) or in air (sand dunes). … As water or air flows into the lee side (downflow side) of an object it slows down, and some of the sediment that was in suspension will settle out.

What is cross-bedding used for?

Cross bedding forms on a sloping surface such as ripple marks and dunes, and allows us to interpret that the depositional environment was water or wind. Examples of these are ripples, dunes, sand waves, hummocks, bars, and deltas.

What is hummocky topography?

‘Hummocky topography’ is a non‐genetic, descriptive term applied to landscapes with irregular hills and depressions. … This term implies that the hummocky topography was formed by the melt‐out and collapse of supraglacial till, during the melting of stagnant ice (Gravenor & Kupch, 1959, Boulton, 1972).

What is a hummocky landscape?

Hummocky (h)

Landscapes with a complex pattern of generally short steep slopes extending from prominent knolls to somewhat rounded depressions or kettles are termed hummocky.

What is hummocky topography quizlet?

hummocky topography. What causes soil creep? barely predictable, non-accelerating downslope movement. Caused by the expansion and contraction of soil as a result of heating and cooling, freezing thawing or wetting and drying.

Where does hummocky cross-stratification occur?

Although hummocky cross-stratification is usually found in shallow marine sedimentary rocks, it has also been found in some lacustrine sedimentary rocks.

What is a hummocky moraine?

hummocky moraine A strongly undulating surface of ground moraine, with a relative relief of up to 100 m, and showing steep slopes and deep, enclosed depressions. It results from the downwasting (i.e. thinning) of ice which is usually stagnant.

What is Swaley cross-stratification?

B: Swaley cross-stratification (SCS) was introduced by Leckie and Walker (1982, p. 143) to describe “a series of superimposed concave-upward shallow scours about 0.5–2 m wide and a few tens of centimeters deep” observed in fine to medium sandstone.

What causes ripple marks to form in sand and mud puddles?

Ripple marks are ridges of sediment that form in response to wind blowing along a layer of sediment. … Ripples may be made by water or, in sand dunes, by wind. The symmetry of water-current ripple marks indicate whether they were formed by gentle waves or faster water currents.

What is ripple cross lamination?

The form of cross-lamination (see crossstratification) produced by the migration of wave-generated ripples, or combined flow ripples (i.e. ripples formed by a combination of wave action and unidirectional flow).

What are climbing ripples?

CLIMBING RIPPLES. Net deposition during ripple formation produces an element of vertical motion of ripple crests as well as an element of horizontal motion. Climbing ripples are formed as a result; require net deposition, as in decelerating flows associated with river floods or turbidity currents.

What is the meaning of the word hummocks?

hummock • HUM-uk • noun. 1 : a rounded knoll or hillock 2 : a ridge of ice 3 : a fertile area in the southern United States and especially Florida that is usually higher than its surroundings and that is characterized by hardwood vegetation and deep humus-rich soil.

What is a sample sentence for hummock?

5. Time after time I stumbled over some hummock of tough grass, and once I went into a creek up to my shoulders. 6. The wide belt of dune-land with its hummocks and scrubby grass growing out of the sand was deserted at that hour.

WHAT IS A hummock Hill?

A hummock is a hill, a mound, or a ridge. This word was once a nautical term describing a hill rising up on a coastline. A hummock is a perfect place for a lighthouse. Today it is either a rounded hill or an elevated place in an ice field.

Are drumlins layered?

Drumlins may comprise layers of clay, silt, sand, gravel and boulders in various proportions; perhaps indicating that material was repeatedly added to a core, which may be of rock or glacial till.

What do eskers record?

Eskers that formed in subglacial tunnels are valuable tools for understanding the nature and evolution glaciers and ice sheets. They record the paths of basal meltwater drainage near to the ice margin. The weight of the overlying ice means that the subglacial meltwater is under high pressure.

How does a Roche Moutonnee form?

In glaciology, a roche moutonnée (or sheepback) is a rock formation created by the passing of a glacier. The passage of glacial ice over underlying bedrock often results in asymmetric erosional forms as a result of abrasion on the “stoss” (upstream) side of the rock and plucking on the “lee” (downstream) side.

What is cross bedding and how does it form?

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 does cross beds indicate?

The cross-beds reflect the steep faces of ripples and dunes. These steep faces tilt down-current and thus indicate current flow direction. Cross-beds are commonly curved at the base; this gives a handy way of determining right-side up in complexly deformed rocks.