How volatility is reflected in candlestick charts:

Length of the wick:

The wicks (shadows) of the candles indicate the maximum and minimum price variation during a period of time. A long wick indicates greater volatility, while a short wick indicates lower volatility.

Candlestick patterns:

Some candlestick patterns, such as the Engulfing pattern or the Doji candle, can indicate changes in volatility or possible trend reversals.

In summary: Trading algorithms can use candlestick charts to identify trading opportunities, but they are not the ones that cause volatility. Volatility is manifested in price movements, and candlestick charts are a visual tool for analyzing that volatility.