The concept of storm rock

Figure 5- 1 storm surge and typhoon

Storms generally refer to strong weather phenomena in the atmosphere, especially weather systems accompanied by strong winds or heavy precipitation. As a meteorological phenomenon, storm is a tropical cyclone developed in tropical and subtropical oceans. Storms in different areas have different characteristics. Storms occurring in the ocean can be divided into tropical storms, mid-latitude storms and polar storms according to geographical latitude; According to the size of the horizontal range, it can also be divided into synoptic scale storms and mesoscale storms; According to different oceans, there are different names such as typhoon, hurricane and tropical storm (Figure 5- 1). Among them, mid-latitude storms mainly include explosive cyclones at sea, and polar storms mainly include polar depression. Tropical storms in the northwest Pacific can be divided into typhoons, strong tropical storms and tropical storms according to the magnitude of wind power. Mesoscale storms mainly include squall lines and tornadoes at sea. The quantitative criteria of tropical storm are roughly as follows: when the surface wind speed of tropical cyclone reaches 17m/s, it is called tropical storm; When the wind speed exceeds 33m/s, it is called hurricane (Atlantic) or typhoon (Pacific). The extratropical cyclone is a winter storm at middle and high latitudes, moving from west to east.

2. The concept of rainstorm flow

Under the action of hurricanes, storm flows often appear in modern oceans. On the one hand, it can form turbulence with a speed of 100 km or even hundreds of km, on the other hand, it has strong wave action. The bottom of this storm wave can be as deep as 200 meters, indicating that the storm flow has the nature of traction current. At the same time, in the vast sea area near the coast and shelf, storm waves can also erode, excavate and transform the bottom sediments (He Jingyu, 1987), disturb the bottom sediments, form suspended clouds in the storm flow, and become density current. Therefore, the rainstorm flow is a kind of density flow, which has the nature of traction current.

Storm surge refers to the shallow sea basin controlled by storm flow. Due to the huge speed of storm wave energy propagation, the seawater rushed to the shore and the tidal surface rose sharply (Meng Xianghua, 1985).

3. The concept of storm rock

Storm rocks refer to sedimentary rocks formed by storm action, which are mainly distributed in shallow seas (lakes) or coastal areas near or above the bottom of storm waves. Tempestite is a turbidite which was proposed by Kelling( 1973) to describe the redeposition in shallow sea basin (Kumar&Sanden, 1978) after being disturbed by storm. Aigner (1979) extended its meaning to storm deposits, which generally refers to a series of sediments formed by abnormal weather storms. Liu Baojun (1984) translated this word into "storm layer", especially the sediment formed by storm waves. Wang (1984) suggested that the new words should be translated into "storm layer" when describing sediments caused by modern storms, and "storm rock" when describing rocks caused by ancient storms, and both should be collectively referred to as "storm deposits".