Natural geographical environment

China Pioneering Area is located in the southwest of CC Area in the Northeast Pacific Basin. Taking Haiyang No.4 fault (NATO150 W, South about147 30 ′ W) as the boundary, the development zone is divided into east and west areas. The geographical coordinates of the East Zone are about 7 ~ 10 north latitude and 0/40 ~149 west longitude, with an area of 79703km2. The geographical coordinates of the western district are roughly 8 ~1n north latitude and 150 ~ 155 west longitude, with an area of 70297km2. The sum of the areas of the east and west parts is 654.38+500,000 square kilometers. The Eastern District and the Western District are 2050km and1800km away from Lulu Port in Honolulu and about10000km away from Guangzhou.

2. 1.2 Hydrometeorological survey

The pioneer area is located in tropical waters, with a lot of precipitation. The climate is hot and humid all the year round, mainly cloudy to cloudy, with an average wind force of 4 ~ 5. There are two systems that have great influence on the weather change: tropical cyclone in the northeast Pacific and intertropical convergence zone. The former has a small probability and a strong influence, and some of them can reach the intensity of typhoon, causing disastrous weather. It should be pointed out that the generation and development time of tropical cyclone (or typhoon) happens to be the best season for offshore operation, which has a great influence, but the time is generally short. The direction of wind waves and swells is similar, mainly small waves and medium swells, in which the waves over 2m are swells, and the peak of big swells is from June to July every year. Generally speaking, the natural conditions are complex and harsh, which is completely different from land mineral exploitation.

The current in the upper layer of the development sea area belongs to the equatorial current system, which develops from north to south into the equatorial current from west to north, from east to north and from west to south in turn. The position and intensity of equatorial airflow system change with the seasons. The northern equatorial airflow affects the northern part of the western region from February to August and moves northward after August; The southern equatorial airflow affects the southern part of the eastern region after August and moves out of the eastern region in February of the following year.

The vertical structure of water temperature, salinity and density in the pioneer area can be divided into mixed layer (< < 70m), thermocline (70 ~ 180~4200m), gradient layer (180~4200m) and uniform layer (> 4200m) from top to bottom.

2. 1.3 seabed landform features

The water depth in the pioneering area is generally 4800~5200m, the elevation difference of seabed topography is 50 ~ 100m, and the elevation difference of seamounts is 500 ~ 1500m. The seabed topography here belongs to the deep-sea hilly area of the Northeast Pacific Basin. The development of seabed topography and geomorphology is controlled by two fault zones, Clarion and Clipperton, and the expanding ocean ridge. The first-class landforms are large seamounts, seamount chains, intermountain basins and deep-sea troughs and valleys, and the strike is northeast or nearly east-west, parallel to the strike of the two major faults. The secondary landforms include low and gentle dike-like uplift, platform, chain-like sea mound and groove. Generally, the distance between hill chains or platform trenches is 5 ~ 10 km, the height difference between hills and depressions is tens of meters to hundreds of meters, and the height difference between platforms and trenches can reach 200 ~ 300 m ... Most of these landforms are NNW-trending or nearly NNW-trending, parallel to the spreading ridge, and cut off by the secondary transform fault which is near east-west or northeast-east. Generally speaking, basement undulation is the main factor to control the topographic characteristics of the seabed. The characteristics of seabed topography and geomorphology in the east and west of the pioneer area are obviously different, belonging to two large topographic and geomorphological units. The western region is characterized by seamount chains and beaded seamounts distributed in the east-west direction, and the topographic features in the east-west direction are more obvious than those in the north-south direction (Figure 2- 1). The eastern region is characterized by alternating NW-trending platforms and trenches, and the NW-trending topographic features are more obvious than NE-trending ones (Figure 2-2).

Figure 2- 1 Submarine Topographic Map of West Zone

Figure 2-2 Submarine Topographic Map of East Zone of Development Zone

Seamount chain, mound chain or platform are usually asymmetric, the former is steep in the north and slow in the south; The latter has a steep eastern slope and a gentle western slope. Cliffs or cliffs often appear on one side of the hillside, and gravel piles, collapses or landslides may also appear at the foot of the steep slope. Obviously, these landform types will become unstable areas or terrain obstacles in mining operations.

From the multi-beam echo sounding (sea beam) color filling map, we can see that there are a series of conical submarine volcanoes with diameters ranging from several kilometers to dozens of kilometers, which are 500 ~ 1500m higher than the seabed. These submarine volcanoes are arranged in order in the west, forming a spectacular east-west seamount chain and beaded seamounts, while they are scattered in the northwest platform trench in the east. The slope of a circular seamount is generally greater than 5.