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Igneous rock

Also called magmatic rock. Rocks formed from molten material from the earth's interior that condenses and solidifies under different geological conditions. Rocks formed when molten lava erupts from volcanic channels and solidifies on the surface are called extrusive rocks or volcanic rocks. Common volcanic rocks include basalt, andesite and rhyolite. Rocks formed when lava rises but does not reach the surface but solidifies at a certain depth in the earth's crust are called intrusive rocks. They are divided into plutonic rocks and epigenetic rocks according to the location of the intrusion. Granite, gabbro, and diorite are typical plutonic rocks. Granite porphyry, gabbro porphyry and diorite porphyry are common epigenetic rocks. According to the chemical composition, igneous rocks can be divided into ultrabasic rocks (SiO2, less than 45), basic rocks (SiO2, 45-52), neutral rocks (SiO2, 52-65), and acidic rocks (SiO2, greater than 65) and alkaline rock (containing special alkaline minerals, SiO 2 , 52-66). Igneous rocks account for 64.7% of the crust's volume. ②

Sedimentary rocks

. Layered rocks are formed by transportation, deposition and diagenesis of weathered materials, volcanic debris, organic matter and a small amount of cosmic materials under normal temperature and pressure conditions on the earth's surface. According to the origin, it can be divided into clastic rocks, clay rocks and chemical rocks (including biochemical rocks). Common sedimentary rocks include sandstone, tuffaceous sandstone, conglomerate, claystone, shale, limestone, dolomite, siliceous rock, iron rock, phosphorous rock, etc. Sedimentary rocks account for 7.9% of the crust's volume, but are widely distributed on the surface of the crust, accounting for about 75% of the land area, and the seafloor is almost entirely covered by sediments. Sedimentary rocks have two outstanding characteristics: First, they have layers, called bedding structures. The interface between layers is called a layer. Usually the rock layer below is older than the rock layer above. Second, many sedimentary rocks contain the remains of "lithic" ancient organisms or traces of their survival and activities - fossils, which are precious materials for determining geological age and studying paleogeographic environments. They are called records of the earth's history. of "pages" and "texts". ③

Metamorphic rock

. Rock formed by metamorphism of original rock. According to different types of metamorphism, metamorphic rocks can be divided into five categories: dynamic metamorphic rocks, contact metamorphic rocks, regional metamorphic rocks, migmatites and metasomatic metamorphic rocks. Common metamorphic rocks include mylonite, cataclastic rock, hornfels, slate, phyllite, schist, gneiss, marble, quartzite, amphibolite, schistite, eclogite, migmatite, etc. . Metamorphic rocks account for 27.4% of the crust's volume. Rocks have specific physical properties such as specific gravity, porosity, compressive strength and tensile strength. They are factors that need to be considered in construction, drilling, excavation and other projects. They are also the carrier of various mineral resources. Different types of rocks contain different mineral. Taking igneous rocks as an example, basic ultrabasic rocks are related to siderophilic elements, such as chromium, nickel, platinum group elements, titanium, vanadium, iron, etc.; acidic rocks are related to lithophile elements such as tungsten, tin, molybdenum, beryllium, lithium, It is related to niobium, tantalum and uranium; diamond is only produced in kimberlite and potash lamprophyre; chromite is mostly produced in dunite; tungsten-tin deposits are abundant in the early Yanshan granite in South China; independent tungsten-tin deposits are often formed in the late Yanshan granite. Tin ore and niobium, tantalum and beryllium deposits. Oil and coal only occur in sedimentary rocks. Iron deposits in Precambrian metamorphic rocks are cosmopolitan. Many rocks themselves are also important industrial raw materials. For example, Beijing's white marble (a kind of white marble) is a well-known building decoration material at home and abroad. Nanjing's Yuhua Stone, Fujian's Shoushan Stone, and Zhejiang's Qingtian Stone are good arts and crafts stones. Even those that are not used by people Note that river sand and pebbles are also very useful building materials. Many rocks are also important raw materials for traditional Chinese medicine. For example, medical stone (a medium-acidic vein rock) is a very popular medicinal rock. Rocks are also an important factor in tourism resources. The world's famous mountains, rivers, peaks and caves are all related to rocks. Our ancestors have been using rocks since the Stone Age. Today, with the rapid development of science and technology, people's clothing, food, shelter, transportation, travel, and medicine... can't be separated from rocks.

The direction of the hillside involves climate and sunshine intensity. For example, the sunny slope of the mountain has stronger sunshine and more rain, while the backside slope of the mountain may not melt ice and snow all year round. Obviously, the weathering characteristics of the rocks are quite different. Erosion and weathering complement each other in nature. Only when rocks are weathered can they be easily eroded. When the rocks are eroded, fresh rocks can be exposed to continue weathering. The transportation of weathering products is the main manifestation of denudation. When rock debris flows with the transport medium, such as wind or water, it will cause erosion on the surface, riverbed and lakeshore zone. This also produces more debris, providing material conditions for sedimentation. Under the action of sunlight, moisture, organisms and air, rocks are gradually destroyed and decomposed into sand and soil, which is called weathering. Sand and soil are the products of rock weathering. 1. The weathering phenomenon of rocks. The loosening, peeling, and cracks of rocks are all phenomena of rock weathering. 2. The causes of weathering of rocks.