Introduction to Geology - Examples & Applications

Introduction to Geology: Worked Applications

All numerical plate velocities and site profiles below are synthetic teaching data. State the reference frame, units and simplifying assumptions before interpreting a result.

$Constant Relative Travel with Millimetres and Millions of Years$

Two points on different plates have a prescribed constant relative speed of $50\ \text{mm/year}$ along one direction. Find their relative travel over $1\ \text{Ma}$ .

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$A Conditional Duration from Travel and Rate$

A reconstruction supplies $1{,}400\ \text{km}$ of relative travel along a specified path. What elapsed interval would correspond to a constant relative speed of $3.5\ \text{cm/year}$ ?

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$Full Spreading Rate from Two Symmetric Flanks$

Each flank moves away from a fixed ridge axis at $15\ \text{mm/year}$ . Under symmetric constant spreading, how long is required to create a total width of $120\ \text{km}$ between the two reference margins?

Opposite flank velocities of 15 mm per year produce a full opening rate of 30 mm per year across 120 km — Two Half Rates Make One Full Rate

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$Two Eastward Velocities in One Reference Frame$

At the initial time, A is $100\ \text{km}$ west of B on one east–west line. In a common fixed frame, A moves east at $20\ \text{mm/year}$ and B east at $50\ \text{mm/year}$ . Find their separation after $2\ \text{Ma}$ .

A moves 40 km and B 100 km east, changing an initial 100 km separation to 160 km — Subtract Common-Frame Velocities

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$Northwest Travel Resolved into Signed Components$

For this exercise, treat a hotspot as fixed. A plate point moves relative to it at $7\ \text{cm/year}$ , azimuth $315^\circ$ clockwise from north, for $2.5\ \text{Ma}$ . Find the east and north displacement components.

A 175 km vector at azimuth 315 degrees has a west component and a north component each 123.744 km — Resolve a Northwest Displacement

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$Oblique Convergence across a North-South Boundary$

A lies west of B across a north–south reference boundary. Their common-frame east/north velocities are A $(10,20)$ and B $(-20,50)\ \text{mm/year}$ . Find the relative vector, speed and motion type.

Subtracting A's velocity from B's gives minus 30 east and plus 30 north mm per year — Normal and Tangential Relative Motion

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$Temperature Increase versus Absolute Ground Temperature$

An illustrative undisturbed profile has $T_0=22\,^\circ\text{C}$ at depth zero and a constant gradient of $25\,^\circ\text{C/km}$ . Estimate the temperature at $40\ \text{m}$ and state what this says about an energy pile.

A Prescribed Depth–Temperature Profile

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$Event Ordering from a Truncated Dike$

In the synthetic section, upright bed B overlies bed A. Dike D cuts both beds but terminates at an erosion surface U. Cap C covers U and is not cut by D. Establish the supported sequence.

Dike D cuts A and B, is truncated at U, and lies beneath uncut cap C — Read the Specific Cross-Cutting Evidence

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$Sedimentary Cover on Foliated Metamorphic Basement$

A borehole and an exposure confirm $15\ \text{m}$ of sandstone deposited on an eroded schist basement. The schist foliation is inclined. Classify the unconformity and identify the next engineering questions for a possible dam.

A 15 metre sandstone cover rests on an eroded schist basement with inclined foliation and unmeasured hydraulic properties — Foliation Is Not the Bedding Test

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$A Linear Ground-Model Hypothesis between Two Boreholes$

Two holes have collars at elevation $100\ \text{m}$ on a flat profile. At station $0\ \text{m}$ , a proposed rock contact is $8\ \text{m}$ deep; at station $200\ \text{m}$ it is $14\ \text{m}$ deep. Estimate its midpoint depth under a straight-line interpretation and identify the uncertainty.