フレノスカンディアの氷河の静止調整に関する空間-地質学的制約
G A Milne1, J L Davis, J X Mitrovica
1Department of Geological Sciences, University of Durham, Durham DH1 3LE, UK. g.a.milne@durham.ac.uk
Science (New York, N.Y.)
|March 27, 2001
まとめ
グローバル・ポジショニング・システム (GPS) のデータは,氷河氷河の同静的調整がフェノスカンディアン地殻の変形を引き起こしていることを示しています. この研究は,地球のモデルを精錬し,地域の海面上昇を推定し,重要な構造的動きを排除します.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- 固体地球 ジオダイナミクス
- 氷河学 氷河学とは
背景:
- フェノスカンディアは,地殻の進行中の変形を経験しています.
- この変形を理解することは,地球科学モデルと海面変化の評価に不可欠です.
研究 の 目的:
- グローバルポジショニングシステム (GPS) のデータを用いてフェノスコンディアの3次元地殻変形を分析する.
- 地質学的データとGPS観測によって制約される地球モデルを開発する.
- 地域的な海面上昇と水平構造運動を推定する.
主な方法:
- GPSデータから3次元地殻変形の分析.
- 地球モデルを開発するためにGPS観測と数値予測を比較する.
- GPSから派生した線形運動をフェノスカンダの潮位計記録と統合した.
- GPSから派生した地表層の速度フィールドに基づいて,水平構造運動の評価.
主要な成果:
- 氷河のイソスタティック調整は,フェノスカンディアの地殻変形の主な要因である.
- この研究は,上層マントルの平均粘度 (5 x 10^20 to 1 x 10^21 Pa s) と石層の弾性厚さ (90170 km) の境界線を提供している.
- 地域の海面上昇は,年間2.1 ± 0.3mmと推定されています.
- 1年あたり約1mmを超える水平構造的動きは排除されています.
結論:
- GPSのデータは,フェノスカンディアの地殻の移動の主な原因として,氷河の静止調整を確認しています.
- 派生した地球モデルは,独立した地質学的制約と一致しています.
- この発見は,マントルの粘度,石層構造,およびこの地域の海面の変化をよりよく理解するのに寄与しています.
関連する概念動画
01:16Electrostatic Boundary Conditions
Consider an external electric field propagating through a homogeneous medium. When the electric field crosses the surface boundary of the medium, it undergoes a discontinuity. The electric field can be resolved into normal and tangential components. The amount by which the field changes at any boundary is given by the difference between the field components above and below the surface boundary.
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
The surface integral of an electric field is given by Gauss's law in integral form and is related to...
01:28Magnetostatic Boundary Conditions
An electric field suffers a discontinuity at a surface charge. Similarly, a magnetic field is discontinuous at a surface current. The perpendicular component of a magnetic field is continuous across the interface of two magnetic mediums. In contrast, its parallel component, perpendicular to the current, is discontinuous by the amount equal to the product of the vacuum permeability and the surface current. Like the scalar potential in electrostatics, the vector potential is also continuous...
01:26Constraints and Statical Determinacy
In structural engineering, the equilibrium of a system is not only determined by its equations of equilibrium but also with the help of constraints. Constraints refer to restrictions on the motion of a system. The proper combinations of constraints can minimize the total number of constraints needed to maintain a system in mechanical equilibrium. When this happens, the system is said to be statically determinate. For such systems, the unknown reaction supports can be estimated using equilibrium...
01:12Temperature Dependent Deformation
In a nonhomogeneous rod made up of steel and brass, restrained at both ends and subjected to a temperature change, several steps are involved in calculating the stress and compressive load. Due to the problem's static indeterminacy, one end support is disconnected, allowing the rod to experience the temperature change freely. Next, an unknown force is applied at the free end, triggering deformations in the rod's steel and brass portions. These deformations are then calculated and added together...
01:26Influence of Earth's Curvature and Atmospheric Refraction on Leveling
During leveling, the Earth's curvature and atmospheric refraction introduce deviations in the line of sight from a true horizontal reference. When the line of sight is leveled, it remains perpendicular to the plumb line only at a single point. Beyond this, it deviates due to the Earth’s curvature, represented by the correction C. For a sight distance D, the deviation can be derived using the relationship:This relationship shows that the deviation increases quadratically with distance. Over a...
01:19Limits with Oscillating Discontinuities
An oscillating discontinuity is a type of discontinuity in which a function’s values fluctuate infinitely often as the input approaches a particular point. Unlike jump discontinuities, where the function suddenly shifts between two values, or infinite discontinuities, where the function diverges without bound, an oscillating discontinuity arises from rapid back-and-forth variation. Because the function never stabilizes toward a single value, no finite limit exists at that point.One of the most...