地球动力学-GEODYNAMICS053板块构造1-2.ppt

360Ma 356Ma 340Ma 320Ma 306Ma * Distribution of epicenters, color-coded to show the corresponding depth of focus /geology/mcconnell/envGeo/Lectures/lect10/lect10.htm#distribution Photo # wrldseismic.gif The places on the earth where major earthquakes occur tend to outline the boundaries between these crustal plates, suggesting that seismic activity can be interpreted as the result of the horizontal movements of the lithospheric plates. * 板块和热点 In 1963, J. Tuzo Wilson, the Canadian geophysicist who discovered transform faults, came up with an ingenious idea that became known as the hotspot theory. 热点 Hot Spot 夏威夷岛链 夏威夷岛链 Hawaii Chain Indications for Mantle Plumes from Seismic Tomography Wolfe et al., 1997 The Gravity Signal of Mantle Plumes Strong central anomaly ~ 80 mgal With a diameter of ~ 150 km - 200 km Sidelobes with a signal ~ 20 to 50 mgal Diameter of the entire patter ~ 500 km The Gravity Signal of Mantle Plumes – Density Anomalies related to Plumes Isostatic gravity anomaly and related isostatic topography: - Thickening of the crust due to volcanic eruptiva and intrusions - Thermal thinning of the lithosphere Positive small wavelength central gravity anomaly - Bending of the lithosphere under the volcanic chain Dynamic gravity anomaly and related dynamic topography: - Thermally reduced density of the hot mantle rocks - Dynamic topography due to the flow pressure of the rising material - Dynamic topography of the Core-Mantle Boundary - Density anomalies related to position change of phase boundaries - Sidelobes of the gravity anomaly Melting related gravity anomalies - Density changes due to petrological changes during melting and Compaction. 3D Numerical model of a Mantle Plume Principal Layout Length: x,y 4000 km, z=3000 km Periodic in horizontal dT : 2100°C   “Reference Model “ visco-plastic rheology 3. Strong phase boundary 火山成因 Volcanoes 太平洋板块的演变 威尔逊 Wilson Cycle 板块运动（空间大地测量） 地幔对流