マントルの流れに対する抵抗は,オーストラリア上部マントルの電磁気衝突から推測される
1Geophysics Institute, University of Göttingen, Germany. f.simpson@gns.cri.nz
Nature
|August 9, 2001
まとめ
地震アニソトロピーは,オーストラリアの上層マントルのオリヴィン (olivine) のa-axesがプレート運動と整合していないことを明らかにします. これは,マントルが構造板の移動による変形に抵抗することを示唆しています.
科学分野:
- 地質物理学 地質物理学とは地質物理学です.
- ミネラル物理学 ミネラル物理学
- テクトニクス (地質学) とは
背景:
- オリヴィンの好ましい方向性によって引き起こされる地震性アニソトロピーは,シーア波分裂によってよく研究されています.
- オリビンの電気伝導性はアニソトロピーも示しているが,上層マントルの研究は稀である.
- マントルフローモデルは,オリヴィン (olivine) のa軸が,単純な剪定下でのプレート運動と並行することを予測しています.
研究 の 目的:
- オーストラリアの下の上層マントルの電気的アニソトロピーを調査するために.
- 電磁気衝撃を絶対的なプレート運動方向と比較するために.
- オリヴィン結晶のa軸とマントルの変形の並び方を推測する.
主な方法:
- オーストラリアの下の上層マントルの電磁画像.
- 地震アニソトロピーと電気伝導性の分析.
- プレートの絶対運動データとの比較.
主要な成果:
- マントルの電磁力衝突とオーストラリアのプレート運動方向の間の大きな不一致が観察されました.
- オリビン結晶のa軸は,現在の絶対プレート運動に平行して並行していない.
- この不整列は,マントルの変形に対する抵抗を示している.
結論:
- オリビンのa軸の平準化とプレート運動の仮定は,普遍的に成立しないかもしれません.
- マントルの変形はプレート運動によってのみ引き起こされるのではなく,他の抵抗力を示唆しています.
- 電気伝導性の研究は,上層マントルの動力学と鉱物組織を理解するために不可欠です.
さらに関連する動画
関連する概念動画
01:19Magnetic Field Lines
5.4K
The representation of magnetic fields by magnetic field lines is very useful in visualizing the strength and direction of the magnetic field. Each of the magnetic field lines forms a closed loop. The field lines emerge from the north pole (N), loop around to the south pole (S), and continue through the bar magnet back to the north pole.
Magnetic field lines follow several hard-and-fast rules:
Magnetic field lines follow several hard-and-fast rules:
5.4K
01:20Momentum And Radiation Pressure
1.8K
An object absorbing an electromagnetic wave would experience a force in the direction of propagation of the wave. This force occurs because electromagnetic waves contain and transport momentum. The force accounts for the wave's radiation pressure exerted on the object. Maxwell's prediction was confirmed in 1903 by Nichols and Hull by precisely measuring radiation pressures with a torsion balance. The measuring instrument had mirrors suspended from a fiber kept inside a glass container.
1.8K
01:23Magnetic Field due to Moving Charges
11.3K
A stationary charge creates and interacts with the electric field, while a moving charge creates a magnetic field.
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
Consider a point charge moving with a constant velocity. Like the electric field, the magnetic field at any point is directly proportional to the magnitude of the charge and inversely proportional to the square of the distance between the source point and the field point. However, unlike the electric field, the magnetic field is always perpendicular to the plane containing the line...
11.3K
01:18Magnetic Flux
4.2K
The magnetic flux measures the number of magnetic field lines passing through a given surface area. The SI unit for magnetic flux is the weber (Wb). Magnetic flux is a scalar quantity. It depends on three factors: the strength of the magnetic field B, the area through which the field lines pass, and the relative orientation of the field with the surface area.
Suppose a surface is divided into elements of area dA. For each element, the component of the magnetic field that is normal to the...
Suppose a surface is divided into elements of area dA. For each element, the component of the magnetic field that is normal to the...
4.2K
01:28Magnetostatic Boundary Conditions
1.9K
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...
1.9K
01:31Magnetic Susceptibility and Permeability
2.9K
In linear magnetic materials, like paramagnets and diamagnets, magnetization is proportional to the magnetic field intensity. The constant of proportionality, a dimensionless number, is called magnetic susceptibility. The value of the susceptibility depends on the type of material.
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
When diamagnetic materials are placed under an external magnetic field, the moments opposite to the field are induced. Hence, the susceptibility for diamagnets has a minimal negative value of 10-5–10-6. Since...
2.9K