From geographic points of views, PengHu Islands have geographical characters as (1)Mesa: hill shape with flat top surrounded by cliffs, the average altitude in PengHu Islands as 20 to 50 meters; （2）Complex shores: small and large islands and rock reef. in PengHu Islands of total area 127 square kilometers and coast length with 320 kilometers, the complex shores can be divided into sea-closed shore, rock shore without cliffs, and sand beach; (3) South high and north low feature.  Aeolian geography are land forms made by actions of winds, such as wind erosion and accretion or mass movement, and water erosive land forms include rain gully and erosive gully.  Sea may beat shores with actions of waves, sea flows, and tides to have erosion, movement, and accretion to shape land forms on coasts, such as erosive cliff, plate form, ladder, column (reef), gully, hole, beach, sand bar, and sand open.  Igneous rock and sedimentary rock are two major ones in PengHu Islands, and HuaYu has metamorphic rocks somewhere.  Igneous rocks are divided into extrusive rocks and intrusive rocks, the former indicates magma clots on ground after spraying out, also called as igneous rocks, and the latter means shaping rocks in deep underground, such as plutonic rock and hypabyssal rocks.  The intrusive rocks in PengHu Islands include veins in ChiMei Yu, veins in Hua Yu, and veins of TienTai Mountain basalt in WangAn Island.   Apart from those intrusive rocks of small amounts, uncovered basalts in PengHu area are extrusive rocks, such as basalt, agglomerated settlement, agglomerate, and tuff.  The sedimentary rocks include conglomerate, sandstone, silt stone, shale, and limestone. Under columnar basalt in PengHu are some uncovered sedimentary rocks, such as ChiMei with the kind of rocks everywhere.   Metamorphic rocks are scattered in Hua Yu, and some of them form due to contact when magma spraying out, such as light color and thin rocks aside of the whale hole in SiaoMen Yu, as metamorphic under heat effects.