Very quickly, the sand sinks to the bottom and the water floats to the top. This is where the salt comes in. When there’s enough salt present, as soon as the clay particles liquefy, electrical charges make them begin to stick together to form bigger particles and these also settle with the sand. Quicksand is a mixture which looks like solid, but behaves more like a liquid.

　　Despite its murderous reputation, quicksand does not such people under and swallow them, although it can hold a person in firm grip. The human body is more buoyant(有浮力) in quicksand than in water, and sooner or later anyone trapped in it will float.

　　Unlike most liquids, quicksand’s viscosity, or “runniness” can suddenly change if it comes under pressure, for example under a human foot. The surface gives way and the victim quickly sinks in up to the knees, surrounded by an area of dirty things that turns semi-solid around its victim. Escaping from the quicksand’s grip(紧握) requires a large amount of force. Without something solid to pull at, people often find they are stuck fast. Pulling at one leg simply makes the other one sink further.

　　So how do you escape from quicksand’s control? Stay still and call for help. Staying still stops you sinking any further, until--with luck--help arrives on the scene. If no one appears and you need to draw yourself out, gently lie down on your back until your body is floating on the sand. Next, roll over onto your stomach and pull yourself forwards with your hands, so that you gradually “swim” towards firmer ground. It is a slow and dirty business, but it works.

【决胜高考 2016高考英语黄金30题：专题06 考前必做难题30题（教师版）】相关文章：

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题22 自然灾害话题指导（教师版）

★ 2014届高考英语一轮复习选修6参考答案（外研版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题21 语言学习话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题17 体育运动话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题05 环境保护话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题15 生活习惯话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题11 青少年成长话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题19 文学艺术话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题06 记叙概括话题指导（教师版）

★ 湖南省长沙县实验中学2016届高三英语二轮复习书面表达复习重点话题指导专题16 素质教育话题指导（教师版）