Milankovitch Cycles and Glacier Period

棉花糖

按：我们爬山的时候，经常会有机会见到冰川，我巧合接触到一些冰川的常识，贴出来，有兴趣的可以看看。（在上个月去Columbia Gorge的时候，谢谢Jinsi MM对地质方面的兴趣和鼓励我多研究，感觉Jinsi的好学，认真的治学精神和对知识的热情探索无止境的态度，积极鼓励了我）

We are currently in the middle of a glacial period (although it’s less intense now than it was 20,000 years ago) but
this is not the only period of glaciation in Earth’s history; there have been many in the distant past。In general, however, Earth has been warm enough to be ice-free for much more of the time than it has been cold enough to be glaciated.

我们目前正处于一个冰期的中期阶段，（虽然现在比二千年前密度低），但是
这不是地球历史上唯一的冰川时期; 在遥远的过去已经有很多冰川期。然而，一般来说，地球已经足够温暖，无法有更多时间，变得更加寒冷，冷得足够形成（新的）冰川了。


The episodic nature of the Earth's glacial and interglacial periods within the present Ice Age (the last couple of million years) have been caused primarily by cyclical changes in the Earth's circumnavigation of the Sun. Variations in the Earth's eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles for Milutin Milankovitch, the Serbian astronomer and mathematician who is generally credited with calculating their magnitude. Taken in unison, variations in these three cycles creates alterations in the seasonality of solar radiation reaching the Earth's surface. These times of increased or decreased solar radiation directly influence the Earth's climate system, thus impacting the advance and retreat of Earth's glaciers.

It is of primary importance to explain that climate change, and subsequent periods of glaciation, resulting from the following three variables is not due to the total amount of solar energy reaching Earth. The three Milankovitch Cycles impact the seasonality and location of solar energy around the Earth, thus impacting contrasts between the seasons.


目前冰河时代（近二百万年）地球冰川和间冰期间的情景性质主要是由于太阳的地球循环变化引起的。地球偏心，轴向倾斜和进动的变化包括三个主要循环，统称为Milutin Milankovitch的Milankovitch循环，塞尔维亚天文学家和数学家，通常被称为计算其大小。一致认为，这三个周期的变化造成太阳辐射到达地球表面的季节性变化。这些增加或减少的太阳辐射时代直接影响着地球的气候系统，从而影响到地球冰川的进退。

        解释以下三个变量导致的气候变化及随后的冰川时期并不是由于太阳能到达地球的总量是最重要的。三个Milankovitch周期影响了地球周围太阳能的季节性和位置，从而影响了季节之间的对比。

棉花糖

Some of the important features visible are arêtes: sharp ridges between U-shaped glacial valleys;
cols: low points along arêtes that constitute passes between glacial valleys; horns: steep peaks that have been
glacially and freeze-thaw eroded on three or more sides; cirques: bowl-shaped basins that form at the head of a
glacial valley; hanging valleys: U-shaped valleys of tributary glaciers that hang above the main valley because
the larger main-valley glacier eroded more deeply into the terrain; and truncated spurs (a.k.a. “spurs”): the ends
of arêtes that have been eroded into steep triangle-shaped cliffs by the glacier in the corresponding main valley.