１． Lithosphere/asthenosphere ２． A number of plates (more than one) ３． Differential movements

• １． Lithosphere/asthenosphere

• ２． A number of plates (more than one)

• ３． Differential movements

• ４． Deformation occurs at plate boundaries

Basic concepts of plate tectonics

Fig.1

Lithosphere＝ strong

Asthenosphere＝ weak

Fig.2

F/s =

F F

= ２ d/dt

d/dt = / ２

Strain L/L

Stress

Strain rate d /dt = /t

viscosity

s: Fractional area

Fig.3

Conductive Earth

Tm

750°C 1300°C

3000 km

0

Fig.4

TemperatureStream lines Temerature averaged at depth

Thermal boundary layer

Thermal boundary layer

Convection

Thermal boundary layer

Fig.5Modified from Parsons and Richter (1981)

Subduction

Oceanic plate

Fig.6

750°C 1300°C

Efficiency of convection vs conduction

Tm

Heatflow q = kdT/dz

Fig.7

Conduction

Convection

3000 km

0

Fig.8

Wiens & Stein (1985)

Earthquakes within oceanic plates

Fig.9

Low velocity zone

Shear-wave velocity (km/s)

Depth

(km)

Anderson & Toksoz (1963)

Fig.10

Free-air gravity anomaly

Load

Lithosphere

Asthenosphere

Continental plate

Oceanic plate

Subduction

VolcanismContinents

No recycling

Recycling

Fig.11

ArcheanProterozoic

Phanerozoic

Fig.12

Continental area growth

Fig.13Pollack (1986)

Hotspot trace

Fig.14Data: ETOP5

Seismicity（ depth<１００ km）

Pacific plate

Eurasian plate

Antarctic plate

N. American plate

S. American plateAfrican plate

Indo-Australian plate

Major platesFig.15

Philippine Sea Pl.

Scotia plate

Cocos plate

Juan de Fuca plate

Nazca plate

Carribean plate

Arabian plate

Minor platesFig.16

Caroline plate

Venus

Fig.17

Saunders et al. (1992)

Mars

Fig.18

Venus: topography

Fig.19Ford & Pettengill (1992)

Earth’s topography

Fig.20NOAA (1985)

Topography distribution of the planets

Fig.21

Warren (1993)

Solomatov & Moresi (1996)

Fig.22

Venus: Stagnant-lid convection