DIASTROPHISM

WHAT IS DIASTROPHISM?

It is the dynamical forces generally tend to elevate the earth’s surface.

It is in constant battle against external forces that tend to wear away the land surface.

TYPES OF EARTH MOVEMENT

UPLIFT Is the movement of the earth wherein

the crust rises.

SUBSIDENCE A sinking or setting of a part of the

earth’s crust with respect to the surrounding parts.

THRUST Horizontal movement of the earth’s

crust.

THEORIES OF DIASTROPHISM

THEORIES OF ISOSTASY

From the Greek word meaning “equal standing”

States that as rock from higher region is removed by erosion and deposited on a lower region, the higher region slowly rises while the lower region becomes heavier and slowly sinks.

CONTRACTION THEORY

It states that the earth is gradually shrinking.

As the shrinkage occurs, the stronger and heavier blocks of the crust sink while the weaker strata are crowded and squeezed upward.

THEORIES OF DIASTROPHISM

CONVECTION THEORY

A theory which would account for the pushing and folding of rocks through convection currents.

This process is true when it occurs under a continental mass.

THEORIES OF DIASTROPHISM

STRUCTURAL FEATURES OF EARTH MOVEMENT

DEFORMATION OF ROCKS

The effects of diastrophism is more clearly seen in rocks, especially in sedimentary rocks.

Any deformation of sedimentary rocks is shown in tilt, bends, or break in layer.

STRUCTURAL FEATURES OF EARTH MOVEMENT

FOLDS

A bend or flexure in a rock can be likened to waves on the ocean.

Each has a crust or upfold and a trough or downfold.

“ANTICLINE” The crust of a rock

“SYNCLINE” The trough of the rock

STRUCTURAL FEATURES OF EARTH MOVEMENT

DIP and STRIKE

DIP The angle between the horizontal plane and a structural surface

STRIKE The direction of a line along the edge of an inclined bed where it meets the horizontal plane,

Always at the right of the dip.

STRUCTURAL FEATURES OF EARTH MOVEMENT

PITCHING FOLD Folds whose axes slant downward at each end of an imaginary line running alone the top of an anticline or along the bottom of a syncline called “AXES of the fold”.

“PITCH” The angel between the axis and the

horizontal.

STRUCTURAL FEATURES OF EARTH MOVEMENT

JOINTS and FISSURES

JOINTS Is a fracture or a little separation between the rock walls

FISSURES Cracks or actual gaps between the rock walls.

STRUCTURAL FEATURES OF EARTH MOVEMENT

FAULTING

It refers to the surface along which a rock body has been broken and has been displaced.

STRUCTURAL FEATURES OF EARTH MOVEMENT

TYPES OF FAULTING

1. VERTICAL FAULTING occurs when an entire block of rock is

raised evenly so that the layers remain in their original horizontal position.

2. HORIZONTAL FAULTING occurs when an entire block of rock is

lowered evenly so that layers remain in their original vertical position.