Do overlying strata subside before/during volcanic exogenous dome emplacement?

Understanding the subsidence of overlying strata during exogenous volcanic dome emplacement

Volcanic exogenous domes, also known as extrusive domes or lava domes, are fascinating geological formations that result from the extrusion of viscous lava onto the Earth’s surface during volcanic eruptions. The emplacement of these domes is a complex process influenced by many factors, including the behavior of the overlying strata. An important aspect of dome emplacement is subsidence of overlying strata, which refers to the downward movement or sinking of surrounding rock layers before or during dome formation. In this article, we will review the phenomenon of overburden subsidence and explore its significance in the context of exogenous volcanic dome emplacement.

The Mechanisms of Overlying Layer Subsidence

The subsidence of overlying strata during volcanic exogenous dome emplacement can be attributed to several mechanisms, which may act individually or in combination. One of the primary causes is the removal of magma from beneath the surface, resulting in a decrease in the support provided by the molten rock. As the magma rises and erupts to form the dome, it creates a void or cavity in the subsurface, causing the overlying strata to subside and fill the void. This subsidence is often observed as a depression or trough surrounding the dome.

Another mechanism that can contribute to subsidence of overlying strata is compaction and consolidation of volcanic materials. During the emplacement of an exogenous dome, the extruded lava accumulates and solidifies, forming a resistant mass. As the lava cools and contracts, it exerts pressure on the surrounding rock layers, causing them to compress and subside. The amount of subsidence depends on several factors, including the volume and thickness of the lava dome and the rheological properties of the surrounding rock.

Effects of subsidence of overlying strata

The subsidence of overlying strata has significant implications for the emplacement of extrusive domes and the hazards associated with them. One of the most important consequences is the creation of potential pathways for magma ascent during subsequent eruptions. The subsided layers can form conduits or channels that facilitate the movement of magma toward the surface, providing a preferential route for future volcanic activity. This phenomenon is known as dike intrusion, where magma uses the weakened zones created by subsidence to reach the surface.

In addition, subsidence of overlying strata can destabilize the surrounding terrain, resulting in the formation of fissures, cracks, or collapse structures. These features can pose hazards such as ground instability, landslides, and even the formation of volcanic sinkholes. In addition, subsidence-induced surface deformation can affect infrastructure, including buildings, roads, and pipelines, causing damage and disruption in volcanic regions.

Field observations and research techniques

To study the subsidence of overlying strata during extrusive dome emplacement, researchers use a variety of field observations and investigative techniques. Geologic mapping of the area surrounding the dome provides valuable information on the distribution and extent of subsidence features. This includes the identification of depressions, faults, and fractures associated with the subsidence of overlying strata.

Geodetic surveys, such as GPS measurements and satellite-based remote sensing techniques, are also critical to monitoring and quantifying subsidence. These methods allow scientists to detect surface deformations with high precision, and thus identify subsidence patterns and rates. In addition, geophysical investigations, such as seismic surveys and ground-penetrating radar, can provide insight into subsurface structures and help elucidate the processes associated with subsidence of overlying strata.
In summary, subsidence of overlying strata plays an important role in the emplacement of exogenous volcanic domes. Understanding the mechanisms and implications of this phenomenon is critical for characterizing volcanic hazards and assessing the potential for future eruptions. By combining field observations with advanced research techniques, scientists continue to deepen their knowledge of overlay subsidence, contributing to the advancement of volcanology and earth science.

FAQs

Do overlying strata subside before/during volcanic exogenous dome emplacement?

Yes, overlying strata can experience subsidence before and during the emplacement of volcanic exogenous domes. Subsidence occurs due to the movement and displacement of magma beneath the surface, which can cause the overlying rocks and sediment to sink.

What causes the subsidence of overlying strata during volcanic exogenous dome emplacement?

The subsidence of overlying strata during volcanic exogenous dome emplacement is primarily caused by the withdrawal of magma from beneath the surface. As magma rises and accumulates beneath the volcano, it can create a void or cavity. This withdrawal of magma leads to the collapse and sinking of the overlying rocks, resulting in subsidence.

Are there any other factors that contribute to the subsidence of overlying strata during volcanic exogenous dome emplacement?

Yes, in addition to the withdrawal of magma, other factors can contribute to the subsidence of overlying strata. These factors include the weight of the growing dome itself, which puts pressure on the underlying rocks, and the release of gases during volcanic activity, which can cause the surrounding rocks to weaken and collapse.

What are the implications of overlying strata subsidence during volcanic exogenous dome emplacement?

The subsidence of overlying strata can have several implications. It can lead to the formation of grabens or depressions on the surface, where the sinking rocks create a visible topographic feature. Subsidence can also cause changes in groundwater flow and can potentially affect the stability of infrastructure and human settlements located above the volcanic system.

Is subsidence of overlying strata a common phenomenon during volcanic exogenous dome emplacement?

Yes, subsidence of overlying strata is a relatively common phenomenon during volcanic exogenous dome emplacement. It is observed in many volcanic systems worldwide where dome-building eruptions occur. However, the extent and magnitude of subsidence can vary depending on the specific characteristics of the volcano and the properties of the overlying rocks.