地质时间尺度

 

Why would you want to name time?
::为什么你要点时间?

When you refer to events in the history of your life you often link it to a time period. "When I was in kindergarten..." might be the start of your story. It helps scientists to have names to refer to events in Earth history. For this reason, they developed the geologic time scale.
::当你提到你生命史上的事件时,你常常把它与一个时间段联系起来。 “当我在幼儿园的时候...” 可能是你故事的开始。 它帮助科学家用名称来表示地球历史中的事件。 因此,他们开发了地质时间尺度。

The Geologic Time Scale
::地质时间尺度

Earth formed 4.5 billion years ago. Geologists  divide  this time span into smaller periods. Many of the divisions mark major events in life history.
::地球在45亿年前形成。地质学家将这一时间分为较小的时期。许多分歧标志着生命史上的重大事件。

Dividing Geologic Time
::divide 地理地理时间

Divisions in Earth's history are recorded on the  geologic time scale . For example, the Cretaceous ended when the non-avian dinosaurs went  extinct . European geologists were the first to put together the geologic time scale. So, many of the names of the time periods are from places in Europe. The Jurassic Period is named for the Jura  Mountains  in France and Switzerland, for example.
::地球历史上的分界线以地质时间尺度记录下来。 例如,当非鸟类恐龙灭绝时,白龙时代就结束了。欧洲地质学家是最早将地质时间尺度拼凑在一起的。因此,许多时间周期的名称来自欧洲各地。例如,侏罗纪时代被命名为法国和瑞士的Jura山。

Putting Events in Order
::将事件按顺序排列

To create the geologic time scale, geologists correlated   layers. Steno's laws were used to determine the relative ages of rocks. Older rocks are at the bottom, and younger rocks are at the top. The early geologic time scale could only show the order of events. The discovery of  radioactivity  in the late 1800s changed that. Scientists could determine the exact age of some rocks in years. They assigned dates to the time scale divisions. For example, the Jurassic began about 200 million years ago. It lasted for about 55 million years.
::为了创建地质时间尺度, 地质学家关联层。 Steno 的法律被用来确定岩石的相对年龄。 年长的岩石位于底部, 较年轻的岩石位于顶部。 早期的地质时间尺度只能显示事件的先后顺序 。 1800年代末发现的放射性改变了这一点 。 科学家可以确定某些岩石的准确年代。 他们指定了时间尺度分区的日期 。 例如, Jurassic 始于大约两亿年前。 它持续了大约5500万年 。

Divisions of the Geologic Time Scale
::地理时间尺度的分区

The largest blocks of time on the geologic time scale are called “eons.” Eons are split into “eras.” Each era is divided into “periods.” Periods may be further divided into “epochs.” Geologists may just use “early” or “late.” An example is “late Jurassic,” or “early Cretaceous.” Pictured below is the geologic time scale ( Figure   ).
::地质时间尺度上最大的时间区块被称为“太阳 ” 。 Eons被分为“时代 ” 。 每个时代被分为“时代 ” 。 时间段可以进一步划分为“时代 ” 。 地质学家可以“早”或“晚 ” 。 一个例子是“大侏罗纪 ” 或“早期白化 ” 。 下面是地质时间尺度(图 ) 。

 

Summary
::摘要

• The geologic time scale divides Earth history into named units. Naming time periods makes it easier to talk about them.
  ::地质时间尺度将地球历史分为名称单位。命名时间段可以更容易地谈论它们。

• The units of the time scale are separated by major events in Earth or life history.
  ::时间尺度的单位由地球或生命史上的重大事件分开。

• In the geologic time scale, time units are divided and subdivided into smaller pieces.
  ::在地质时间尺度中,时间单位被划分成小块,再细分为小块。

Review
::回顾

1. Why do Earth scientists need a geologic time scale?
   ::为什么地球科学家需要一个地质时间尺度?

1. Why are some units of the geologic time scale longer and some shorter?
   ::为什么一些地质时间尺度的单位更长,一些更短?

1. What did the discovery of radioactivity do to change the geological time scale?
   ::放射性的发现会改变地质时间尺度吗?