CHAPTER IX.

THE MOVEMENTS AND DEFORMATIONS OF THE EARTH’S BODY (DIASTROPHISM).

+Minute and Rapid Movements+ 526 _Earthquakes_ 527 Points of origin, foci, 527. The amplitude of the vibrations, 529. Destructive effects, 530. Direction of throw, 531. Rate of propagation, 532. Sequences of vibrations, 533. Gaseous emanations, 533. Distribution of earthquakes, 533. _The Geologic Effects of Earthquakes_ 534 Fracturing of rock, 534. Changes of surface, 534. Effects on drainage, 535. Effects on standing water, 535. Changes of level, 536.

+Slow Massive Movements+ 537 Present movements, 538. Fundamental conceptions, 539.

_Nearly Constant Small Movements_ 540 Reciprocal features, 541.

_The Great Periodic Movements_ 542 Mountain-forming movements, 542. Distribution of folded ranges, 543. Plateau-forming movements, 543. Continent-forming movements, 544. Relations of these movements in time, 545. Relations of vertical to horizontal movements, 545. The squeezed segments, 546. The depressed or master segments, 546. The differential extent of crustal movements, 548.

+The Causes of Movement+ 551 _General Considerations_ 551 1. _The centripetal agencies_ 552 Gravity, 552. Molecular and sub-molecular attractions, 554. Cohesion and crystallization, 554. Diffusion, 555. Chemical combination, 556. Sub-atomic forces 556. 2. _The resisting agencies_ 557 Heat, 557. All resistance perhaps due to motion, 558.

+Alternative Views of Original Heat Distribution+ 559 Thermal distribution on the convection hypothesis, 559. Level of no stress, 561. Thermal distribution on the hypothesis of central solidification, 562. Thermal distribution under the accretion hypothesis, 564. _Computed Pressures, Densities, and Temperatures within the Earth Based on Laplace’s Law_ 564 Recombination of material, 568. Comparison of the hypotheses, 568.

+Observed Temperatures in Excavations+ 569 Explanations of varying increment, 570. The permeation and circulation of water, 570. Chemical action, 570. Differences in the conductivity of rock, 571. Compression, 571. Gradients projected, 571. The amount of loss of heat, 572. The amount of shrinkage from loss of heat, 572.

+Other Sources of Deformation+ 574 Transfer of internal heat, 574. Denser aggregation of matter, 574. Extravasation of lavas, 574. Change in the rate of rotation, 575. Distribution of rigidity, 578.

_Sphericity as a Factor in Deformation_ 580 The influence of the domed form of the surface, 581. Theoretical strength of domes of earth-dimensions, 581. Stress-accumulation independent of sphericity, 583. The actual configuration of the surface, 584. Concave tracts, 584. General conclusion, 588.