Know : A list of the oldest rivers on Earth

Meuse RiverThe age of a river is difficult to determine. Generally, the age is estimated based upon which mountains are the source of the river, the age of any mountains it dissects, the sea or ocean to which it eventually outflows, and where it forms its delta. For instance, if a river dissects a mountain range, then this often means the river existed before the mountain range rose.

Each of these factors can make a final contribution in determining the age of a river. Below follows an incomplete list of rivers older than 1 Ma (One million years = 1,000,000 years).

Continent color key
Africa Asia Oceania Europe North America South America
River Age (Ma) Outflow Most significant criterion for the age
1. 380 North Sea Paleozoic, dissects the Ardennes during the Hercynian
2. 350-400 Lake Eyre
(intermittent)
Predates the Alice Springs Orogeny; many other rivers in the Northern Territory are of a similar age
2.

(Chang Jiang)

365 East China Sea Crosses Paleozoic and Mesozoic mountains
3.
(Kanawha River)
300 Kanawha River Dissects the Appalachian Mountains
4. Susquehanna River 300 Chesapeake Bay Dissects the Appalachian Mountains
5. Nile 250 Mediterranean Sea Mesozoic
6. Rhine 240 North Sea Triassic, maybe older because of the Hercynian; not the Eocene with the Alps, nor the Miocene with the Upper Rhine Graben
7. Save 205 Indian Ocean Formed during rifting when Gondwana broke up.
8. Amazon 200 Atlantic Ocean Jurassic, but it seems to have flowed in the opposite direction as an extension of the Congo, i.e. long before the formation of Andes
9. Amur 125 Sea of Okhotsk Known to be at least Cretaceous in age, but crosses mountains even older
10. Macleay River 80 Tasman Sea Predates uplift of Great Escarpment
11. Murrumbidgee River 75 Murray River Predates uplift of Australian Alps
12. Colorado
(Western U.S.)
75 Gulf of California Uplift during Laramide orogeny, see Geology of the Grand Canyon area
13. Thames 58 North Sea Late Palaeocene Period Thanetian Stage.
14.

(Sindhu)

45 Arabian Sea Source in the Himalayas and Karakoram Mountains

Courtesy : Wikipedia

 

Know : World’s Largest Desert Sahara? NO! :)

Know : World’s Largest Desert Sahara? NO! 🙂

More Facts and Amazing Pics below….

sahara

The origins of the Sahara desert, the largest hot desert in the world, dated back to approximately 600 million years ago. The sea submerged the region over and over again, depositing its sediments; whenever it resurfaced, it was alternately covered by forests, savannahs and even marshlands. During that time, trees, such as oaks, cypresses, olive trees and Aleppo pines, grew in the area. Approximately 50-55 million years ago, these lands surfaced once and for all and the land started to get dry, as many finds still attest: shells, trunks now turned into stone after a long silicification process, wall paintings and graffito portraying the typical fauna of the savannah.

The Sahara Desert is located in the northern portion of Africa and covers over 3,500,000 square miles (9,000,000 sq km) or roughly 10% of the continent (image). It is bounded in the east by the Red Sea and it stretches west to the Atlantic Ocean. To the north, the Sahara Desert’s northern boundary is the Mediterranean Sea, while in the south it ends at the Sahel, an area where the desert landscape transforms into a semi-arid tropical savanna.

Since the Sahara Desert makes up nearly 10% of the African continent, the Sahara is often cited as the world’s largest desert. This is not entirely true, however, as it is only the world’s largest hot desert. Based on the definition of a desert as an area receiving less than 10 inches (250 mm) of precipitation per year, the world’s largest desert is actually the continent of Antarctica at 5,339,573 sq mi (13,829,430 sq km).

Geography of the Sahara Desert

The Sahara covers parts of several African nations including Algeria, Chad, Egypt, Libya, Mali, Mauritania, Morocco, Niger, Sudan and Tunisia. Most of the Sahara Desert is undeveloped and features a varied topography. Most of its landscape has been shaped over time by wind and includes sand dunes, sand seas called ergs, barren stone plateaus, gravel plains, dry valleys and salt flats. Around 25% of the desert is sand dunes, some of which reach over 500 ft (152 m) in height.

There are also several mountain ranges within the Sahara and many are volcanic. The highest peak found in these mountains is Emi Koussi, a shield volcano that rises to 11,204 ft (3,415 m). It is a part of the Tibesti Range in northern Chad. The lowest point in the Sahara Desert is in Egypt’s Qattera Depression at -436 ft (-133 m) below sea level.

Most of the water found in the Sahara today is in the form of seasonal or intermittent streams. The only permanent river in the desert is the Nile River that flows from Central Africa to the Mediterranean Sea. Other water in the Sahara is found in underground aquifers and in areas where this water reaches the surface, there are oases and sometimes small towns or settlements like the Bahariya Oasis in Egypt and Ghardaïa in Algeria.

Since the amount of water and topography varies based on location, the Sahara Desert is divided into different geographic zones. The center of the desert is considered hyper-arid and has little to no vegetation, while the northern and southern portions have sparse grasslands, desert shrub and sometimes trees in areas with more moisture.

Climate of the Sahara Desert

Although hot and extremely dry today, it is believed that the Sahara Desert has undergone various climatic shifts for the last few hundred thousand years. For example, during the last glaciation, it was bigger than it is today because precipitation in the area was low. But from 8000 BCE to 6000 BCE, precipitation in the desert increased because of the development of low pressure over ice sheets to its north. Once these ice sheets melted however, the low pressure shifted and the northern Sahara dried out but the south continued to receive moisture due to the presence of a monsoon.

Around 3400 BCE, the monsoon moved south to where it is today and the desert again dried out to the state it is in today. In addition, the presence of the Intertropical Convergence Zone, ITCZ, in the southern Sahara Desert prevents moisture from reaching the area, while storms north of the desert stop before reaching it as well. As a result, the annual rainfall in the Sahara is below 2.5 cm (25 mm) per year.

In addition to being extremely dry, the Sahara is also one of the hottest regions in the world. The average annual temperature in the desert is 86°F (30°C) but during the hottest months temperatures can exceed 122°F (50°C), with the highest temperature ever recorded at 136°F (58°C) in Aziziyah, Libya.

Plants and Animals of the Sahara Desert

Due to the high temperatures and arid conditions of the Sahara Desert, the plant life in the Sahara Desert is sparse and includes only around 500 species. These consist mainly of drought and heat resistant varieties and those adapted to salty conditions (halophytes) where there is sufficient moisture.

The harsh conditions found in the Sahara Desert have also played a role in the presence of animal life in the Sahara Desert. In the central and driest part of the desert there are around 70 different animal species, 20 of which are large mammals like the spotted hyena. Other mammals include the gerbil, sand fox and Cape hare. Reptiles like the sand viper and the monitor lizard are present in the Sahara as well.

People of the Sahara Desert

It is believed that people have inhabited the Sahara Desert since 6000 BCE and earlier. Since then, Egyptians, Phoenicians, Greeks and Europeans have been among the peoples in the area. Today the Sahara’s population is around 4 million with the majority of the people living in Algeria, Egypt, Libya, Mauritania and Western Sahara.

Most of the people living in the Sahara today do not live in cities; instead they are nomads who move from region to region throughout the desert. Because of this, there are many different nationalities and languages in the region but Arabic is most widely spoken. For those who do live in cities or villages on fertile oases, crops and the mining of minerals like iron ore (in Algeria and Mauritania) and copper (in Mauritania) are important industries that have allowed population centers to grow.

Courtesy : Geography.about.com and respective photographers.

sahara desert sand dunes

Erg Chebbi 1 by Ayme B.

sahara desert

Journey by Angela Kauffman

Sahara Silhouette

Sahara Silhouette by Elise Hibbard

sahara desert blue berber men

Blue Berber men by ZenzPhotography

Sahara Sands

Sahara Sands II by Alicia Elliott

Diplomats discover charm of Tunisian Sahara

Diplomats discover charm of Tunisian Sahara by Magharebia

Sombra de camellos sahara desert

Sombra de camellos by Guillén Pérez

Marocco Morocco sahara desert

Marocco

Dunaren gainean sahara desert

Dunaren gainean by Mr. Theklan

dune sahara desert

dune3 by Laurent Bouclier

como hormigas sahara desert

como hormigas by bachmont

Algerian Dune sahara desert

Algerian Dune 3 by Viva NOLA

Morocco - Sahara - Nomade

Morocco – Sahara – Nomade by Celso FLORES

duna sahara desert

duna by Flávio Eiró

beetle sahara desert

Wandering by Hasna Lahmini

Sahra desert

Sahra by Hasna Lahmini

sahara sand dunes

Dreams and Solace by paintednegative

Sahara desert

Sahara by Alicia Elliott

The Road sahara desert

The Road by Fahad.m

Erg Chebbi sahara desert

Erg Chebbi by Julio Gago

Oasi di montagna (Tunisia) desert oasis

Oasi di montagna (Tunisia) by Francesco Sgroi

sahara desert dune

fine line by Martin Fisch

algeria camels sahara desert

algeria camels by albatros11

Golden Sand - white Desert sahara

Golden Sand – white Desert by Alfonso Ianni

fotógrafo sahara desert

fotógrafo by bachmont

sahara sandstorm

Relief by Hartwig HKD

sahara desert

Hombre de azul en Merzouga by Guillén Pérez