Page 260 - Global Tectonics

CONTINENTAL TRANSFORMS AND STRIKE-SLIP FAULTS 245

Vy

10 mm a -1 km 500 km 400 Lateral strain rates 40 Convergent strain rates 40 thermal anomaly developed

40 mm a -1 200 + + 0 200 0 200 Evolved stage:

(i)
) Vy (mma -1 (k) Shortening component

Pacific Plate 350°C Mantle 120 160 V y 160 120 (km) V z 120 160 (km) Lateral component

elevation Vx 8 Pacific 80 80 Distance 80 Distance
Australia Constant 6 4 40 40 2 -2 40

Elastic 2 30 20 6 4 Single oblique structure
N 10
0 (h) 0 (j) 0
(g) 10 30 50 10 30 50 10 30 50

Vy Depth (km) Depth (km) (l) Figure 8.24 Mechanical model of oblique compression between two plates involving a two-layered crust above mantle lithosphere (images provided by P. Koons and modified from Koons et al., 2003, with permission from the Geological Society of America). (a) Initial model where crust is dragged along its base at velocities of 40 mm a −1 parallel to the y-axis (V y ) and 10 mm a −1 parallel to the x-axis (V x ). Crustal rheology is horizontal and not yet

10 mm a -1 km 500 km 400 Lateral strain rates 40 Convergent strain rates 40 thermal weakening associated with exhumation and concentrated erosion. At this stage both lateral and convergent components of motion are

40 mm a -1 200 (c) + 0 200 (e) 200 0 Initial stage: no thermal anomaly

)
160
Pacific Plate 350°C Mantle 120 V Vy (mma -1 y 120 160 (km) V z 120 160 (km) accommodated along a single dipping structure in the upper crust (l) and may separate in the lower crust.

elevation Main divide Vx 8 Pacific 80 80 Distance 80 Distance
Australia Constant 6 40 30 40 -1 -2 40

Elastic 4 2 20 3 2 1
N 10
(a) 0 (b) 0 (d) 0
x 30 50 30 50
y 10 10 (f)

Depth (km)
Depth (km)

z