The Sunday Observer Magazine brought to you such geological marvels
as Delicate Arch, USA in previous weeks. Stone arches and natural
bridges are some of the most incredible geological phenomena in the
world, brought to you by the hand of time, supported by the weathering
action of wind and water. Time marches inexorably on, however, and the
same forces that built up these exquisite natural wonders will someday
sweep all of them away.
At 77 metres (250 feet) Aloba Arch is the longest known natural arch
outside the United States. Where it surpasses most other natural arches
is in height: a stunning 120 metres or 394 feet. Like the arches of the
American southwest, Aloba Arch is made from hard sandstone hundreds of
millions of years old. It’s located in the Ennedi Range which rises out
of the Sahara Desert in the northeast part of Chad near the border with
Libya and Sudan.
The Sahara Desert abounds with natural arches and stone bridges.
Aloba Arch may be one of the best known but the above bipod arch in
Algeria is worth special mention due to its unusual beauty and exquisite
fragility. Though 1.9 metres (6.23 ft) high, the arch’s thinner leg is a
mere 15 cm (6 inches) thick. How much longer can it last?
Rainbow Bridge, USA
Rainbow Bridge in southern Utah State is the world’s largest natural
bridge. Although well known to local native tribes, the spectacular
sandstone structure was not investigated by American researchers until
the early years of the 20th century. This was partly due to the
isolation of the structure, a fact remedied by the creation of Lake
Powell and its tributary waterways.
Incorporated into Rainbow Bridge National Monument in 1910, Rainbow
Bridge stands 88 m (290 ft) tall, has an 84 metre (275 ft) span and is
13 metres (42 ft) thick at its top point.
Durdle Door, United Kingdom
If the name “Durdle Door” sounds English, well, that’s because it’s
found in southern England along Dorset’s delightfully named Jurassic
Coast. Durdle Door is not so much a door as a window, though, through
which the chill waters of the English Channel pour through.
The headland that includes Durdle Door is made of Portland Limestone,
a material harder than the clays and silts it protects but itself not
impervious to the pounding of the waves. Durdle Door is destined to yawn
ever wider until one day, its roof will fall in and one side becomes an
island in the channel.
Immortal Bridge, China
On
the steep slopes of Mt. Tai in China’s Shandong province, you’ll find
the Immortal Bridge. Hopefully you won’t be forced to cross it on the
way to complete your journey. Looking like a scene from an Indiana Jones
flick, the Immortal Bridge is formed from massive stone blocks
precariously balanced against one another.
Should a strong earthquake jostle the region, the bridge – and anyone
crossing it – would be thrown into the deep gorge at the base of Mt Tai.
Immortality, it would seem, is a relative thing.
webecoist.com
Pont d’Arc, France
In the south of France, the river Ardèche has worn through an
escarpment of ancient limestone forming the Pont d’Arc. This scenic
natural bridge measures 60 metres (197 ft) wide and is 45 metres (147.5
ft) in height.
The Pont d’Arc is a popular tourist attraction as the limestone rock
in the region houses a number of prehistoric sites and caves, such as
the famed Chauvet Cave. The town of Vallon-Pont-d’Arc normally is home
to about 2,000 people but that figure increases by a factor of 10 in the
summer months.
Aloba Arch, Chad 
The Sunday Observer Magazine brought to you such geological marvels
as Delicate Arch, USA in previous weeks. Stone arches and natural
bridges are some of the most incredible geological phenomena in the
world, brought to you by the hand of time, supported by the weathering
action of wind and water. Time marches inexorably on, however, and the
same forces that built up these exquisite natural wonders will someday
sweep all of them away. 
The Sahara Desert abounds with natural arches and stone bridges.
Aloba Arch may be one of the best known but the above bipod arch in
Algeria is worth special mention due to its unusual beauty and exquisite
fragility. Though 1.9 metres (6.23 ft) high, the arch’s thinner leg is a
mere 15 cm (6 inches) thick. How much longer can it last? 
Rainbow Bridge in southern Utah State is the world’s largest natural
bridge. Although well known to local native tribes, the spectacular
sandstone structure was not investigated by American researchers until
the early years of the 20th century. This was partly due to the
isolation of the structure, a fact remedied by the creation of Lake
Powell and its tributary waterways. 
If the name “Durdle Door” sounds English, well, that’s because it’s
found in southern England along Dorset’s delightfully named Jurassic
Coast. Durdle Door is not so much a door as a window, though, through
which the chill waters of the English Channel pour through. 
On
the steep slopes of Mt. Tai in China’s Shandong province, you’ll find
the Immortal Bridge. Hopefully you won’t be forced to cross it on the
way to complete your journey. Looking like a scene from an Indiana Jones
flick, the Immortal Bridge is formed from massive stone blocks
precariously balanced against one another. 
In the south of France, the river Ardèche has worn through an
escarpment of ancient limestone forming the Pont d’Arc. This scenic
natural bridge measures 60 metres (197 ft) wide and is 45 metres (147.5
ft) in height. 
