Name a source of horizontal stress in tectonics.

Name a source of horizontal stress in tectonics.

• A. Gravity
• B. Overburden
• C. Thermal Expansion
• D. Poisson's Ratio Effect

Answer: (D)

Vertical loading from overlying rocks doesn’t just press downward; the rock’s response is tied across directions by Poisson’s ratio. When the crust is compressed vertically under the weight of the overburden, it tends to contract or expand laterally according to its Poisson’s ratio. If the sides are constrained, that vertical strain is converted into horizontal stress, producing horizontal tectonic stress. This coupling between vertical strain and horizontal stress is captured by the Poisson’s ratio effect, making it the best explanation for a source of horizontal stress. Gravity and overburden describe the vertical load that creates the stress field, not the mechanism that generates horizontal stress itself. Thermal expansion can cause stress under constraint, but the direct, characteristic source of horizontal stress in crustal tectonics is the Poisson’s ratio coupling.

Vertical loading from overlying rocks doesn’t just press downward; the rock’s response is tied across directions by Poisson’s ratio. When the crust is compressed vertically under the weight of the overburden, it tends to contract or expand laterally according to its Poisson’s ratio. If the sides are constrained, that vertical strain is converted into horizontal stress, producing horizontal tectonic stress. This coupling between vertical strain and horizontal stress is captured by the Poisson’s ratio effect, making it the best explanation for a source of horizontal stress.

Gravity and overburden describe the vertical load that creates the stress field, not the mechanism that generates horizontal stress itself. Thermal expansion can cause stress under constraint, but the direct, characteristic source of horizontal stress in crustal tectonics is the Poisson’s ratio coupling.