hanoi vietnam 65 trieu nam
The land of Thang Long- HaNoi Vietnam -Dong history of long life. Over the time "beach pool princess bride," To date, geologists have tried to Vietnam to restore many of the changes.

However, if further back every few hundred million years, at a time when the Earth was wild roses are my changes, when the display is still raging dinosaurs, the resource is not allowed.

The closer this day, the evidence collected more and more levels to restore accurate. Thus, history can be divided into the regions of local flexibility of this masterpiece to the stage of research.

1. Crust structure in Hanoi

According to geologists, the Earth's crust is the top but the thickness of the crust is not uniform in different regions. On the continent of its average thickness is 35 km, 10 km below the minimum, maximum is 70 km.

Such difference depends on the altitude of the terrain: the mountains where it has the greatest thickness can reach 70 km (1.1%), the delta between 35-45km (up from 0.47 to 0 , 7%), while on the ocean floor thickness this peak is 10 km (up 0.15%).

If ocean areas, including its water layer, the thickness is only about 20km (up 0.30%).

The surface distribution of the lower crust with depth (called the mantle of the Earth) is called on Mohorovich (name of a geophysicist with the former Yugoslavia) and called Moho surface.

Thanks to the seismic data and gravity as well as the structure itself of the rocks, is divided into continental crust and oceanic crust type. Crust is composed of three layers of material of different density.

Continental crust has an average density 2700 kg/m3 and is divided into different classes are: basalt layer, layer "granite" and sediments.

Generally, the lower part of the crust are two classes: basalt and granite, in the upper sediment layers form the foundation of the territory.

At the HaNoi Vietnam, on the Moho is the northwest - southeast extends to the southeast of the northern gulf coast and northwest of the Vietnam-China border at Lao Cai region.

So thick crust along this zone may also change. In the Tien Hai (Pacific), its value reaches about 28-30km, at the Hanoi area reached about 32-34km, and in Lao Cai region reaches 40-42km.

Foundations before Kainozoi of Hanoi and the surrounding area with a very complex and is located at different depths.

This foundation is the damage and fracture depth is divided into several blocks moving relative to each other both vertically and horizontally in the direction and the formation Kainozoi were coated with different thickness.

2. Period before Kainozoi (formerly Third period, about 65 million years ago)

Kainozoi period before the period form the solid foundation of Vietnam's territory, the northern plains, including the land of Thang Long-Ha Noi-Dong. This stage lasts a few hundred million years.

The geological features and landforms of this period is explained by the evidence remains today and is associated with the evolutionary history of the Delta.

It rocks exposed in the hills, low mountains of Phu Tho Province and the rest sank below the delta area of ​​the city of Hanoi.

2.1. Stratigraphy

The oldest geological formations of this period largely fall into the modern topographic surface.

Currently, the ancient metamorphic rock is composed of gneis, marble, quartzite, amphibolite ... only in boreholes in the North, East England North West town.

The stones are arranged into flowing river floor was created before the Cambrian (N-P1sc) million years old from 1000 to 520 million years ago.

Next, the participants make up the foundation trenches consolidation of hollow place in Hanoi, there are a creation of the University of Central students (Mesozoic).

Within the territory of Hanoi, the formation is also exposed on the steep slopes and adjacent Soc Son District.

That's the kind of continental sedimentary rocks erupted raw mix is ​​deposited in shallow marine coastal environment in an age Trias, Jurassic and Cretaceous Central University students (Mesozoic) today to 200 million years or less.

Among these formations must be mentioned are:

- The stones of the old village system Kun-storey mid-Triassic (T2kl), to this day over 200 million years. It is the original green stone (sand, powder, powder containing volcanic fall, with the eruption lenses acid (trachit, ryotit porphyr and felsit) distribution of the mountain in Ve Linh Mount Dom, Mount Store Forest, mountain birds, pigs Mount Ham, Double Mountain. total thickness of the layer system is from 650-845m.

- System Na Qu is the stone floor of an age between Triassic (T2 nk), is transferred from the stone floor of the system to Khon Village, a 200 million year on this day, distributed in the northern mountain range in western North Soc Son District.

The lower part of the system is the sandstone layer, powder, light gray clay, moved to the top mainly sandstone, gray powder and red-brown clay. The rock contains a lot of fossil foot axes. The formation of Na Qu floor system has a total thickness of 600-940m.

- Ha Coi tier system. The rocks of Early Jurassic age tier system - between (J1-2hc), also by about 150-200 million years today.

The stone floor of the system is exposed discontinuously in a narrow area of ​​low hills west of errors Hien Tan Dan Ninh and Soc Son District.

The composition of the rocks are pebbles, gravel, grit and breccia lenticular, coarse-grained sandstone layers of gray-brown, pale yellow. The whole floor is 120 meters thick.

- Lung Tam tier system. The volcanic rocks ryodacit, ryolit porphyr gray of the schistosity forced us to this old story late Jurassic - Early Cretaceous reveal a narrow area, distributed in the Nam Cuong, Hien Luong, also director of Soc Son District. The thickness of the ice observed around 100m.

Thus, the total thickness of sedimentary formations in the Great Central was born on the territory of Hanoi at about 2,000.

The layered rocks are composed of dislocation and later create small fold or be divided into blocks to move relative to each other by the fracture.

In rocks of volcanic origin containing kaolin minerals. Regarding time, this is the last geological period in the formation of the solid foundation of Thang Long-Ha Noi-Dong.

To achieve the state's solid foundation, this country has gone through many ups and downs transformed by different tectonic cycle. In the operation of the Red River fault system plays a very important role.

Before the occurrence of local subsidence of the trench lying on the stage Kainozoi Hanoi, Red River valley area in particular and the majority of the territory of North Vietnam is generally a block of continental unity was the separation process and denudation by the operation of surface water.

That's why there are no geological formations that early age Paleogen (Paleogen - or about 60 to nearly 50 million years ago) to participate on the design of foundation trenches in lowland sites in Hanoi.

2.2. Tectonic

According to the geologists call, the first stage Kainozoi, local pride lowland Hanoi has undergone several phases (cycles) of different tectonic.

Each tectonic cycles are started by the phenomenon of subsidence and sediment accumulation process will occur, then raised and the phenomenon occurs denudation process.

Therefore, in this period (which can last for thousands of millions of years - from the Precambrian to Triassic) has happened many such cycles.

However, the phenomenon of cycles were repeated after the first cycle, but at a higher level, more complex and more and more complete.

So far, the literature on the history of low-lying local tectonic trenches Hanoi in the period before Kainozoi still very poor, because of the low-lying hard nails are also located at a depth of 5,000 m to above.

The formations involved in nail texture also vary in age and lithological composition. Therefore, to have a right to comment on this issue, the current document is not allowed.

But an important thing to consider is, at this stage Chay River fault system, the Red River fault ... existing and long-term operation so far, so many geologists have called the Red River fault system (common to the fracture on) of a kind multi-cycle through the process of formation and development of simple to the complex of the northern lowland sites in general and Hanoi in particular proud.

If the expression of all phenomena and tectonic processes in the period lasting for billions of years will be very much.

Therefore, on the basis of the collected material, can come to the conclusion that the tectonic evolution of low-lying local pride in Hanoi before Kainozoi period is the period of preparation and complete hardware facilities initial decision to create pictures of areas Hanoi today - that is accumulated on to the next stage of Kainozoi there are sudden qualitative.

 





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