Siccar Point - the world's most important geological site and the birthplace of modern geology

May 12, 2020    Comment   

Siccar Point - the world's most important geological site and the birthplace of modern geology

Siccar Point is world-famous as the most important unconformity described by James Hutton (1726-1797) in support of his world-changing ideas on the origin and age of the Earth.

James Hutton unconformity with annotations - Siccar Point

In 1788, James Hutton first discovered Siccar Point, and understood its significance. It is by far the most spectacular of several unconformities that he discovered in Scotland, and very important in helping Hutton to explain his ideas about the processes of the Earth.At Siccar Point, gently sloping strata of 370-million-year-oldFamennian LateDevonianOld RedSandstone and a basal layer of conglomerate overlie near vertical layers of 435-million-year-old lowerSilurianLlandovery Epoch greywacke, with an interval of around 65 million years.

Standing on the angular unconformity at Siccar Point (click to enlarge). Photo: Chris Rowan, 2009

As above, with annotations. Photo: Chris Rowan, 2009

Hutton used Siccar Point to demonstrate the cycle of deposition, folding, erosion and further deposition that the unconformity represents. He understood the implication of unconformities in the evidence that they provided for the enormity of geological time and the antiquity of planet Earth, in contrast to the biblical teaching of the creation of the Earth.

How the unconformity at Siccar Point formed.

At this range, it is easy to spot that the contact between the two units is sharp, but it is not completely flat. Furthermore, the lowest part of the overlying Old Red Sandstone contains fragments of rock that are considerably larger than sand; some are at least as large as your fist, and many of the fragments in this basal conglomerate are bits of the underlying Silurian greywacke. These are all signs that the greywackes were exposed at the surface, being eroded, for a considerable period of time before the Old Red Sandstone was laid down on top of them.

The irregular topography and basal conglomerate show that this is an erosional contact. Photo: Chris Rowan, 2009

The Siccar Point which is a rocky promontory in the county of Berwickshire on the east coast of Scotland.

Factors Controlling the Shape of a River Delta

May 02, 2020    Comment   

Factors Controlling the Shape of a River Delta

What is a Delta?

A delta is an accumulation of sediments on the mouth of a river which could encompass a community of distributary channels, wetlands, bars, tidal flats, herbal levees and seashores that commonly shift from on location to any other. Delta shape relies of dominant modern conditions where the mouth of the river: tide-, sea wave-, and hurricane-ruled.

Lena River Delta, Siberia.

Factors that control the shape of a River Delta?

River deltas around the world are very exclusive. The form of a river delta is controlled by means of a range of factors which includes:

? The quantity of river discharge.

? The volume of sediment being deposited in a delta place.

? Flowers cover in delta regions capable of trapping sediments.

? Tidal range conditions wherein the river enters the ocean.

? Hurricane-associated weather and oceanographic conditions.

? Coastal geography (mountains or plains) in coastal areas.

? Human interest is now a dominant aspect influencing the form of river deltas.

Yellow River Delta, China

Nile River Delta, Egypt.

River deltas just like the Amazon and Indus Rivers discharge into the sea wherein a high tidal variety affect flow into and out of the mouth of the rivers. Some river delta area are fantastically effected via erosion consequences of storms and excessive wave strength. Infrequent but severe superstorms impact the shape of deltas and shoreline, which includes the effect of hurricanes on the Gulf Coast.

Indus River Delta, Pakistan

Human hobby is chargeable for the abnormal form of the Birdfoot Delta on the Mississippi River created by using the constant dredging to keep shipping channels clear. The production of dams and diversion of water out of the Colorado River has basically shut of the supply of water and sediment to the Colorado River Delta inside the Gulf of California.

The Mississippi Birdfoot Delta is largely controlled by Human activities

Changes to Mississippi River Delta over the last 4000 years ago.

A river no more. Very little water makes it to the Colorado River Delta

Thanks to Dr. Phil Stoffer for supporting in publishing this text.